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Loans | 6 Months Ended
--- | ---
Jun. 30, 2018
Receivables [Abstract] |
Loans | Loans The period end loan composition was as follows.
| June 30, 2018(a) |  | December 31, 2017
| ($ in Thousands)
Commercial and industrial | $ | 7,109,796 |  |  | $ | 6,399,693 |
Commercial real estate — owner occupied | 888,330 |  |  | 802,209 |
Commercial and business lending | 7,998,126 |  |  | 7,201,902 |
Commercial real estate — investor | 3,996,415 |  |  | 3,315,254 |
Real estate construction | 1,487,159 |  |  | 1,451,684 |
Commercial real estate lending | 5,483,574 |  |  | 4,766,938 |
Total commercial | 13,481,700 |  |  | 11,968,840 |
Residential mortgage | 8,207,253 |  |  | 7,546,534 |
Home equity | 911,363 |  |  | 883,804 |
Other consumer | 376,470 |  |  | 385,813 |
Total consumer | 9,495,086 |  |  | 8,816,151 |
Total loans | $ | 22,976,786 |  |  | $ | 20,784,991 |
(a) Includes $16 million of purchased credit-impaired loans The following table presents commercial and consumer loans by credit quality indicator at June 30, 2018.
| Pass |  | Special Mention |  | Potential Problem |  | Nonaccrual |  | Total
| ($ in Thousands)
Commercial and industrial | $ | 6,763,557 |  |  | $ | 92,286 |  |  | $ | 172,177 |  |  | $ | 81,776 |  |  | $ | 7,109,796 |
Commercial real estate - owner occupied | 814,769 |  |  | 16,033 |  |  | 38,879 |  |  | 18,649 |  |  | 888,330 |
Commercial and business lending | 7,578,326 |  |  | 108,319 |  |  | 211,056 |  |  | 100,425 |  |  | 7,998,126 |
Commercial real estate - investor | 3,885,535 |  |  | 59,587 |  |  | 24,790 |  |  | 26,503 |  |  | 3,996,415 |
Real estate construction | 1,452,888 |  |  | 29,559 |  |  | 3,168 |  |  | 1,544 |  |  | 1,487,159 |
Commercial real estate lending | 5,338,423 |  |  | 89,146 |  |  | 27,958 |  |  | 28,047 |  |  | 5,483,574 |
Total commercial | 12,916,749 |  |  | 197,465 |  |  | 239,014 |  |  | 128,472 |  |  | 13,481,700 |
Residential mortgage | 8,141,803 |  |  | 199 |  |  | 2,355 |  |  | 62,896 |  |  | 8,207,253 |
Home equity | 897,471 |  |  | 792 |  |  | 142 |  |  | 12,958 |  |  | 911,363 |
Other consumer | 375,624 |  |  | 706 |  |  | 6 |  |  | 134 |  |  | 376,470 |
Total consumer | 9,414,898 |  |  | 1,697 |  |  | 2,503 |  |  | 75,988 |  |  | 9,495,086 |
Total | $ | 22,331,647 |  |  | $ | 199,162 |  |  | $ | 241,517 |  |  | $ | 204,460 |  |  | $ | 22,976,786 |
The following table presents commercial and consumer loans by credit quality indicator at December 31, 2017.
| Pass |  | Special Mention |  | Potential Problem |  | Nonaccrual |  | Total
| ($ in Thousands)
Commercial and industrial | $ | 6,015,884 |  |  | $ | 157,245 |  |  | $ | 113,778 |  |  | $ | 112,786 |  |  | $ | 6,399,693 |
Commercial real estate - owner occupied | 723,291 |  |  | 14,181 |  |  | 41,997 |  |  | 22,740 |  |  | 802,209 |
Commercial and business lending | 6,739,175 |  |  | 171,426 |  |  | 155,775 |  |  | 135,526 |  |  | 7,201,902 |
Commercial real estate - investor | 3,266,389 |  |  | 24,845 |  |  | 19,291 |  |  | 4,729 |  |  | 3,315,254 |
Real estate construction | 1,421,504 |  |  | 29,206 |  |  | — |  |  | 974 |  |  | 1,451,684 |
Commercial real estate lending | 4,687,893 |  |  | 54,051 |  |  | 19,291 |  |  | 5,703 |  |  | 4,766,938 |
Total commercial | 11,427,068 |  |  | 225,477 |  |  | 175,066 |  |  | 141,229 |  |  | 11,968,840 |
Residential mortgage | 7,490,860 |  |  | 426 |  |  | 1,616 |  |  | 53,632 |  |  | 7,546,534 |
Home equity | 868,958 |  |  | 1,137 |  |  | 195 |  |  | 13,514 |  |  | 883,804 |
Other consumer | 384,990 |  |  | 652 |  |  | — |  |  | 171 |  |  | 385,813 |
Total consumer | 8,744,808 |  |  | 2,215 |  |  | 1,811 |  |  | 67,317 |  |  | 8,816,151 |
Total | $ | 20,171,876 |  |  | $ | 227,692 |  |  | $ | 176,877 |  |  | $ | 208,546 |  |  | $ | 20,784,991 |
Factors that are important to managing overall credit quality are sound loan underwriting and administration, systematic monitoring of existing loans and commitments, effective loan review on an ongoing basis, early identification of potential problems, and appropriate allowance for loan losses, allowance for unfunded commitments, nonaccrual, and charge off policies. For commercial loans, management has determined the pass credit quality indicator to include credits that exhibit acceptable financial statements, cash flow, and leverage. If any risk exists, it is mitigated by the loan structure, collateral, monitoring, or control. For consumer loans, performing loans include credits that are performing in accordance with the original contractual terms. Loans are considered past due if the required principal and interest payments have not been received as of the date such payments were due. Special mention credits have potential weaknesses that deserve management’s attention. If left uncorrected, these potential weaknesses may result in deterioration of the repayment prospects for the credit. Potential problem loans are considered inadequately protected by the current net worth and paying capacity of the obligor or the collateral pledged. These loans generally have a well-defined weakness, or weaknesses, that may jeopardize liquidation of the debt and are characterized by the distinct possibility that the Corporation will sustain some loss if the deficiencies are not corrected. Lastly, management considers a loan to be impaired when it is probable that the Corporation will be unable to collect all amounts due according to the original contractual terms of the note agreement, including both principal and interest. Management has determined that commercial and consumer loan relationships that have nonaccrual status or have had their terms restructured in a troubled debt restructuring meet this impaired loan definition. Commercial loans classified as special mention, potential problem, and nonaccrual are reviewed at a minimum on a quarterly basis, while pass and performing rated credits are reviewed on an annual basis or more frequently if the loan renewal is less than one year or if otherwise warranted. The following table presents loans by past due status at June 30, 2018.
| Current |  | 30-59 Days Past Due |  | 60-89 Days Past Due |  | 90 Days or More Past Due(a) |  | Nonaccrual(b) |  | Total
| ($ in Thousands)
Commercial and industrial | $ | 7,027,210 |  |  | $ | 407 |  |  | $ | 181 |  |  | $ | 222 |  |  | $ | 81,776 |  |  | $ | 7,109,796 |
Commercial real estate - owner occupied | 869,488 |  |  | 193 |  |  | — |  |  | — |  |  | 18,649 |  |  | 888,330 |
Commercial and business lending | 7,896,698 |  |  | 600 |  |  | 181 |  |  | 222 |  |  | 100,425 |  |  | 7,998,126 |
Commercial real estate - investor | 3,969,084 |  |  | 828 |  |  | — |  |  | — |  |  | 26,503 |  |  | 3,996,415 |
Real estate construction | 1,465,850 |  |  | 19,765 |  |  | — |  |  | — |  |  | 1,544 |  |  | 1,487,159 |
Commercial real estate lending | 5,434,934 |  |  | 20,593 |  |  | — |  |  | — |  |  | 28,047 |  |  | 5,483,574 |
Total commercial | 13,331,632 |  |  | 21,193 |  |  | 181 |  |  | 222 |  |  | 128,472 |  |  | 13,481,700 |
Residential mortgage | 8,135,016 |  |  | 9,158 |  |  | 183 |  |  | — |  |  | 62,896 |  |  | 8,207,253 |
Home equity | 891,135 |  |  | 6,534 |  |  | 736 |  |  | — |  |  | 12,958 |  |  | 911,363 |
Other consumer | 372,984 |  |  | 972 |  |  | 763 |  |  | 1,617 |  |  | 134 |  |  | 376,470 |
Total consumer | 9,399,135 |  |  | 16,664 |  |  | 1,682 |  |  | 1,617 |  |  | 75,988 |  |  | 9,495,086 |
Total | $ | 22,730,767 |  |  | $ | 37,857 |  |  | $ | 1,863 |  |  | $ | 1,839 |  |  | $ | 204,460 |  |  | $ | 22,976,786 |
(a) | The recorded investment in loans past due 90 days or more and still accruing totaled $2 million at June 30, 2018 (the same as the reported balances for the accruing loans noted above).
(b) | Of the total nonaccrual loans, $141 million or 69% were current with respect to payment at June 30, 2018.
The following table presents loans by past due status at December 31, 2017.
| Current |  | 30-59 Days Past Due |  | 60-89 Days Past Due |  | 90 Days or More Past Due(a) |  | Nonaccrual(b) |  | Total
| ($ in Thousands)
Commercial and industrial | $ | 6,286,369 |  |  | $ | 170 |  |  | $ | 101 |  |  | $ | 267 |  |  | $ | 112,786 |  |  | $ | 6,399,693 |
Commercial real estate - owner occupied | 779,421 |  |  | 48 |  |  | — |  |  | — |  |  | 22,740 |  |  | 802,209 |
Commercial and business lending | 7,065,790 |  |  | 218 |  |  | 101 |  |  | 267 |  |  | 135,526 |  |  | 7,201,902 |
Commercial real estate - investor | 3,310,000 |  |  | 374 |  |  | — |  |  | 151 |  |  | 4,729 |  |  | 3,315,254 |
Real estate construction | 1,450,459 |  |  | 168 |  |  | 83 |  |  | — |  |  | 974 |  |  | 1,451,684 |
Commercial real estate lending | 4,760,459 |  |  | 542 |  |  | 83 |  |  | 151 |  |  | 5,703 |  |  | 4,766,938 |
Total commercial | 11,826,249 |  |  | 760 |  |  | 184 |  |  | 418 |  |  | 141,229 |  |  | 11,968,840 |
Residential mortgage | 7,483,350 |  |  | 9,186 |  |  | 366 |  |  | — |  |  | 53,632 |  |  | 7,546,534 |
Home equity | 863,465 |  |  | 5,688 |  |  | 1,137 |  |  | — |  |  | 13,514 |  |  | 883,804 |
Other consumer | 382,186 |  |  | 1,227 |  |  | 780 |  |  | 1,449 |  |  | 171 |  |  | 385,813 |
Total consumer | 8,729,001 |  |  | 16,101 |  |  | 2,283 |  |  | 1,449 |  |  | 67,317 |  |  | 8,816,151 |
Total | $ | 20,555,250 |  |  | $ | 16,861 |  |  | $ | 2,467 |  |  | $ | 1,867 |  |  | $ | 208,546 |  |  | $ | 20,784,991 |
(a) | The recorded investment in loans past due 90 days or more and still accruing totaled $2 million at December 31, 2017 (the same as the reported balances for the accruing loans noted above).
(b) | Of the total nonaccrual loans, $135 million or 65% were current with respect to payment at December 31, 2017.
The following table presents impaired loans individually evaluated under ASC Topic 310, excluding $16 million of purchased credit-impaired loans, at June 30, 2018.
| Recorded Investment |  | Unpaid Principal Balance |  | Related Allowance |  | Average Recorded Investment |  | Interest Income Recognized
| ($ in Thousands)
Loans with a related allowance |  |  |  |  |  |  |  |  |
Commercial and industrial | $ | 75,928 |  |  | $ | 77,873 |  |  | $ | 17,628 |  |  | $ | 70,082 |  |  | $ | 725 |
Commercial real estate — owner occupied | 15,386 |  |  | 15,853 |  |  | 829 |  |  | 15,649 |  |  | 95 |
Commercial and business lending | 91,314 |  |  | 93,726 |  |  | 18,457 |  |  | 85,731 |  |  | 820 |
Commercial real estate — investor | 15,397 |  |  | 15,469 |  |  | 4,132 |  |  | 15,485 |  |  | 901 |
Real estate construction | 448 |  |  | 523 |  |  | 77 |  |  | 456 |  |  | 15 |
Commercial real estate lending | 15,845 |  |  | 15,992 |  |  | 4,209 |  |  | 15,941 |  |  | 916 |
Total commercial | 107,159 |  |  | 109,718 |  |  | 22,666 |  |  | 101,672 |  |  | 1,736 |
Residential mortgage | 39,926 |  |  | 44,171 |  |  | 6,208 |  |  | 39,433 |  |  | 863 |
Home equity | 9,817 |  |  | 10,809 |  |  | 3,514 |  |  | 9,917 |  |  | 282 |
Other consumer | 1,049 |  |  | 1,051 |  |  | 109 |  |  | 1,051 |  |  | 1 |
Total consumer | 50,792 |  |  | 56,031 |  |  | 9,831 |  |  | 50,401 |  |  | 1,146 |
Total loans(a) | $ | 157,951 |  |  | $ | 165,749 |  |  | $ | 32,497 |  |  | $ | 152,073 |  |  | $ | 2,882 |
Loans with no related allowance |  |  |  |  |  |  |  |  |
Commercial and industrial | $ | 35,065 |  |  | $ | 47,914 |  |  | $ | — |  |  | $ | 39,201 |  |  | $ | (286 | )
Commercial real estate — owner occupied | 4,869 |  |  | 5,920 |  |  | — |  |  | 4,179 |  |  | 24 |
Commercial and business lending | 39,934 |  |  | 53,834 |  |  | — |  |  | 43,380 |  |  | (262 | )
Commercial real estate — investor | 984 |  |  | 1,031 |  |  | — |  |  | 1,006 |  |  | — |
Real estate construction | — |  |  | — |  |  | — |  |  | — |  |  | — |
Commercial real estate lending | 984 |  |  | 1,031 |  |  | — |  |  | 1,006 |  |  | — |
Total commercial | 40,918 |  |  | 54,865 |  |  | — |  |  | 44,386 |  |  | (262 | )
Residential mortgage | 11,543 |  |  | 11,862 |  |  | — |  |  | 7,839 |  |  | 128 |
Home equity | 1,275 |  |  | 1,289 |  |  | — |  |  | 785 |  |  | 12 |
Other consumer | — |  |  | — |  |  | — |  |  | — |  |  | — |
Total consumer | 12,818 |  |  | 13,151 |  |  | — |  |  | 8,624 |  |  | 140 |
Total loans(a) | $ | 53,736 |  |  | $ | 68,016 |  |  | $ | — |  |  | $ | 53,010 |  |  | $ | (122 | )
Total |  |  |  |  |  |  |  |  |
Commercial and industrial | $ | 110,993 |  |  | $ | 125,787 |  |  | $ | 17,628 |  |  | $ | 109,283 |  |  | $ | 439 |
Commercial real estate — owner occupied | 20,255 |  |  | 21,773 |  |  | 829 |  |  | 19,828 |  |  | 119 |
Commercial and business lending | 131,248 |  |  | 147,560 |  |  | 18,457 |  |  | 129,111 |  |  | 558 |
Commercial real estate — investor | 16,381 |  |  | 16,500 |  |  | 4,132 |  |  | 16,491 |  |  | 901 |
Real estate construction | 448 |  |  | 523 |  |  | 77 |  |  | 456 |  |  | 15 |
Commercial real estate lending | 16,829 |  |  | 17,023 |  |  | 4,209 |  |  | 16,947 |  |  | 916 |
Total commercial | 148,077 |  |  | 164,583 |  |  | 22,666 |  |  | 146,058 |  |  | 1,474 |
Residential mortgage | 51,469 |  |  | 56,033 |  |  | 6,208 |  |  | 47,272 |  |  | 991 |
Home equity | 11,092 |  |  | 12,098 |  |  | 3,514 |  |  | 10,702 |  |  | 294 |
Other consumer | 1,049 |  |  | 1,051 |  |  | 109 |  |  | 1,051 |  |  | 1 |
Total consumer | 63,610 |  |  | 69,182 |  |  | 9,831 |  |  | 59,025 |  |  | 1,286 |
Total loans(a) | $ | 211,687 |  |  | $ | 233,765 |  |  | $ | 32,497 |  |  | $ | 205,083 |  |  | $ | 2,760 |
(a) | The net recorded investment (defined as recorded investment, net of the related allowance) of the impaired loans represented 77% of the unpaid principal balance at June 30, 2018.
The following table presents impaired loans individually evaluated under ASC Topic 310 at December 31, 2017.
| Recorded Investment |  | Unpaid Principal Balance |  | Related Allowance |  | Average Recorded Investment |  | Interest Income Recognized
| ($ in Thousands)
Loans with a related allowance |  |  |  |  |  |  |  |  |
Commercial and industrial | $ | 81,649 |  |  | $ | 83,579 |  |  | $ | 10,838 |  |  | $ | 58,494 |  |  | $ | 2,629 |
Commercial real estate — owner occupied | 23,796 |  |  | 23,937 |  |  | 2,973 |  |  | 12,124 |  |  | 736 |
Commercial and business lending | 105,445 |  |  | 107,516 |  |  | 13,811 |  |  | 70,618 |  |  | 3,365 |
Commercial real estate — investor | 17,823 |  |  | 17,862 |  |  | 1,597 |  |  | 16,924 |  |  | 1,694 |
Real estate construction | 467 |  |  | 578 |  |  | 86 |  |  | 484 |  |  | 29 |
Commercial real estate lending | 18,290 |  |  | 18,440 |  |  | 1,683 |  |  | 17,408 |  |  | 1,723 |
Total commercial | 123,735 |  |  | 125,956 |  |  | 15,494 |  |  | 88,026 |  |  | 5,088 |
Residential mortgage | 40,561 |  |  | 42,922 |  |  | 6,512 |  |  | 40,411 |  |  | 1,614 |
Home equity | 10,250 |  |  | 10,986 |  |  | 3,718 |  |  | 10,521 |  |  | 549 |
Other consumer | 1,135 |  |  | 1,138 |  |  | 122 |  |  | 1,140 |  |  | 3 |
Total consumer | 51,946 |  |  | 55,046 |  |  | 10,352 |  |  | 52,072 |  |  | 2,166 |
Total loans(a) | $ | 175,681 |  |  | $ | 181,002 |  |  | $ | 25,846 |  |  | $ | 140,098 |  |  | $ | 7,254 |
Loans with no related allowance |  |  |  |  |  |  |  |  |
Commercial and industrial | $ | 60,595 |  |  | $ | 82,839 |  |  | $ | — |  |  | $ | 89,275 |  |  | $ | 492 |
Commercial real estate — owner occupied | 2,438 |  |  | 2,829 |  |  | — |  |  | 1,948 |  |  | 36 |
Commercial and business lending | 63,033 |  |  | 85,668 |  |  | — |  |  | 91,223 |  |  | 528 |
Commercial real estate — investor | 1,295 |  |  | 1,295 |  |  | — |  |  | — |  |  | 45 |
Real estate construction | — |  |  | — |  |  | — |  |  | — |  |  | — |
Commercial real estate lending | 1,295 |  |  | 1,295 |  |  | — |  |  | — |  |  | 45 |
Total commercial | 64,328 |  |  | 86,963 |  |  | — |  |  | 91,223 |  |  | 573 |
Residential mortgage | 6,925 |  |  | 7,204 |  |  | — |  |  | 4,999 |  |  | 217 |
Home equity | 641 |  |  | 645 |  |  | — |  |  | 540 |  |  | 7 |
Other consumer | — |  |  | — |  |  | — |  |  | — |  |  | — |
Total consumer | 7,566 |  |  | 7,849 |  |  | — |  |  | 5,539 |  |  | 224 |
Total loans(a) | $ | 71,894 |  |  | $ | 94,812 |  |  | $ | — |  |  | $ | 96,762 |  |  | $ | 797 |
Total |  |  |  |  |  |  |  |  |
Commercial and industrial | $ | 142,244 |  |  | $ | 166,418 |  |  | $ | 10,838 |  |  | $ | 147,769 |  |  | $ | 3,121 |
Commercial real estate — owner occupied | 26,234 |  |  | 26,766 |  |  | 2,973 |  |  | 14,072 |  |  | 772 |
Commercial and business lending | 168,478 |  |  | 193,184 |  |  | 13,811 |  |  | 161,841 |  |  | 3,893 |
Commercial real estate — investor | 19,118 |  |  | 19,157 |  |  | 1,597 |  |  | 16,924 |  |  | 1,739 |
Real estate construction | 467 |  |  | 578 |  |  | 86 |  |  | 484 |  |  | 29 |
Commercial real estate lending | 19,585 |  |  | 19,735 |  |  | 1,683 |  |  | 17,408 |  |  | 1,768 |
Total commercial | 188,063 |  |  | 212,919 |  |  | 15,494 |  |  | 179,249 |  |  | 5,661 |
Residential mortgage | 47,486 |  |  | 50,126 |  |  | 6,512 |  |  | 45,410 |  |  | 1,831 |
Home equity | 10,891 |  |  | 11,631 |  |  | 3,718 |  |  | 11,061 |  |  | 556 |
Other consumer | 1,135 |  |  | 1,138 |  |  | 122 |  |  | 1,140 |  |  | 3 |
Total consumer | 59,512 |  |  | 62,895 |  |  | 10,352 |  |  | 57,611 |  |  | 2,390 |
Total loans(a) | $ | 247,575 |  |  | $ | 275,814 |  |  | $ | 25,846 |  |  | $ | 236,860 |  |  | $ | 8,051 |
(a) | The net recorded investment (defined as recorded investment, net of the related allowance) of the impaired loans represented 80% of the unpaid principal balance at December 31, 2017.
Troubled Debt Restructurings (“Restructured Loans”) Loans are considered restructured loans if concessions have been granted to borrowers that are experiencing financial difficulty. The following table presents nonaccrual and performing restructured loans by loan portfolio.
| June 30, 2018 |  | December 31, 2017
| Performing Restructured Loans |  | Nonaccrual Restructured Loans(a) |  | Performing Restructured Loans |  | Nonaccrual Restructured Loans(a)
| ($ in Thousands)
Commercial and industrial | $ | 32,438 |  |  | $ | 155 |  |  | $ | 30,047 |  |  | $ | 1,776 |
Commercial real estate — owner occupied | 3,820 |  |  | — |  |  | 3,989 |  |  | — |
Commercial real estate — investor | 372 |  |  | 14,268 |  |  | 14,389 |  |  | — |
Real estate construction | 222 |  |  | 226 |  |  | 310 |  |  | 157 |
Residential mortgage | 17,934 |  |  | 20,372 |  |  | 17,068 |  |  | 18,991 |
Home equity | 7,900 |  |  | 2,972 |  |  | 7,705 |  |  | 2,537 |
Other consumer | 1,037 |  |  | 12 |  |  | 1,110 |  |  | 25 |
Total | $ | 63,723 |  |  | $ | 38,005 |  |  | $ | 74,618 |  |  | $ | 23,486 |
(a) | Nonaccrual restructured loans have been included within nonaccrual loans.
The Corporation had a recorded investment of approximately $4 million in loans modified in troubled debt restructurings during the six months ended June 30, 2018, of which less than $1 million were in accrual status and approximately $4 million were in nonaccrual pending a sustained period of repayment. The following table provides the number of loans modified in a troubled debt restructuring by loan portfolio during the six months ended June 30, 2018 and 2017, respectively, and the recorded investment and unpaid principal balance as of June 30, 2018 and 2017, respectively.
| Six Months Ended June 30, 2018 |  | Six Months Ended June 30, 2017
| Number of Loans |  | Recorded Investment(a) |  | Unpaid Principal Balance(b) |  | Number of Loans |  | Recorded Investment(a) |  | Unpaid Principal Balance(b)
| ($ in Thousands)
Commercial and industrial | 1 |  |  | $ | 47 |  |  | $ | 47 |  |  | 24 |  |  | $ | 30,935 |  |  | $ | 52,260 |
Commercial real estate — owner occupied | — |  |  | — |  |  | — |  |  | 2 |  |  | 716 |  |  | 716 |
Commercial real estate — investor | 1 |  |  | 984 |  |  | 1,031 |  |  | — |  |  | — |  |  | — |
Residential mortgage | 10 |  |  | 2,064 |  |  | 2,064 |  |  | 36 |  |  | 2,695 |  |  | 2,805 |
Home equity | 10 |  |  | 935 |  |  | 949 |  |  | 26 |  |  | 674 |  |  | 919 |
Other consumer | 1 |  |  | 5 |  |  | 8 |  |  | — |  |  | — |  |  | — |
Total | 23 |  |  | $ | 4,035 |  |  | $ | 4,099 |  |  | 88 |  |  | $ | 35,020 |  |  | $ | 56,700 |
(a) | Represents post-modification outstanding recorded investment.
(b) | Represents pre-modification outstanding recorded investment.
Restructured loan modifications may include payment schedule modifications, interest rate concessions, maturity date extensions, modification of note structure (A/B Note), non-reaffirmed Chapter 7 bankruptcies, principal reduction, or some combination of these concessions. During the six months ended June 30, 2018, restructured loan modifications of commercial and industrial, commercial real estate, and real estate construction loans primarily included maturity date extensions and payment schedule modifications. Restructured loan modifications of home equity and residential mortgage loans primarily included maturity date extensions, interest rate concessions, non-reaffirmed Chapter 7 bankruptcies, or a combination of these concessions for the six months ended June 30, 2018. The following table provides the number of loans modified in a troubled debt restructuring during the previous twelve months which subsequently defaulted during the six months ended June 30, 2018 and 2017, respectively, as well as the recorded investment in these restructured loans as of June 30, 2018 and 2017, respectively.
| Six Months Ended June 30, 2018 |  | Six Months Ended June 30, 2017
| Number of Loans |  | Recorded Investment |  | Number of Loans |  | Recorded Investment
| ($ in Thousands)
Commercial and industrial | 3 |  |  | $ | — |  |  | — |  |  | $ | — |
Residential mortgage | 8 |  |  | 2,219 |  |  | 17 |  |  | 941 |
Home equity | 21 |  |  | 1,409 |  |  | 9 |  |  | 271 |
Total | 32 |  |  | $ | 3,628 |  |  | 26 |  |  | $ | 1,212 |
All loans modified in a troubled debt restructuring are evaluated for impairment. The nature and extent of the impairment of restructured loans, including those which have experienced a subsequent payment default, is considered in the determination of an appropriate level of the allowance for loan losses. Allowance for Credit Losses The allowance for credit losses is comprised of the allowance for loan losses and the allowance for unfunded commitments. The level of the allowance for loan losses represents management’s estimate of an amount appropriate to provide for probable credit losses in the loan portfolio at the balance sheet date. The allowance for unfunded commitments is maintained at a level believed by management to be sufficient to absorb estimated probable losses related to unfunded credit facilities (including unfunded loan commitments and letters of credit) and is included in accrued expenses and other liabilities on the consolidated balance sheets. See Note 12 for additional information on the allowance for unfunded commitments. The following table presents a summary of the changes in the allowance for loan losses by portfolio segment for the six months ended June 30, 2018.
($ in Thousands) | Commercial and industrial | Commercial real estate - owner occupied | Commercial real estate - investor | Real estate construction | Residential mortgage | Home equity | Other consumer | Total
December 31, 2017 | $ | 123,068 |  | $ | 10,352 |  | $ | 41,059 |  | $ | 34,370 |  | $ | 29,607 |  | $ | 22,126 |  | $ | 5,298 |  | $ | 265,880 |
Charge offs | (19,611 | ) | (1,042 | ) | (1,202 | ) | (53 | ) | (956 | ) | (1,729 | ) | (2,488 | ) | (27,081 | )
Recoveries | 6,406 |  | 287 |  | 21 |  | 290 |  | 690 |  | 1,192 |  | 416 |  | 9,302 |
Net Charge offs | (13,205 | ) | (755 | ) | (1,181 | ) | 237 |  | (266 | ) | (537 | ) | (2,072 | ) | (17,779 | )
Provision for loan losses | 750 |  | 1,213 |  | 4,272 |  | (5,455 | ) | 1,796 |  | (301 | ) | 2,225 |  | 4,500 |
June 30, 2018 | $ | 110,613 |  | $ | 10,810 |  | $ | 44,150 |  | $ | 29,152 |  | $ | 31,137 |  | $ | 21,288 |  | $ | 5,451 |  | $ | 252,601 |
Allowance for loan losses |  |  |  |  |  |  |  |
Individually evaluated for impairment | $ | 17,628 |  | $ | 829 |  | $ | 4,132 |  | $ | 77 |  | $ | 6,208 |  | $ | 3,514 |  | $ | 109 |  | $ | 32,497 |
Collectively evaluated for impairment | 92,985 |  | 9,981 |  | 40,018 |  | 29,075 |  | 24,929 |  | 17,774 |  | 5,342 |  | 220,104 |
Acquired and accounted for under ASC 310-30(a) | — |  | — |  | — |  | — |  | — |  | — |  | — |  | — |
Total allowance for loan losses | $ | 110,613 |  | $ | 10,810 |  | $ | 44,150 |  | $ | 29,152 |  | $ | 31,137 |  | $ | 21,288 |  | $ | 5,451 |  | $ | 252,601 |
Loans |  |  |  |  |  |  |  |
Individually evaluated for impairment | $ | 110,993 |  | $ | 20,255 |  | $ | 16,381 |  | $ | 448 |  | $ | 51,469 |  | $ | 11,092 |  | $ | 1,049 |  | $ | 211,687 |
Collectively evaluated for impairment | 6,996,038 |  | 866,356 |  | 3,969,829 |  | 1,486,464 |  | 8,154,904 |  | 900,187 |  | 375,421 |  | 22,749,199 |
Acquired and accounted for under ASC 310-30(a) | 2,765 |  | 1,719 |  | 10,205 |  | 247 |  | 880 |  | 84 |  | — |  | 15,900 |
Total loans | $ | 7,109,796 |  | $ | 888,330 |  | $ | 3,996,415 |  | $ | 1,487,159 |  | $ | 8,207,253 |  | $ | 911,363 |  | $ | 376,470 |  | $ | 22,976,786 |
(a) | Loans acquired in business combinations and accounted for under ASC Subtopic 310-30 "Receivables — Loans and Debt Securities Acquired with Deteriorated Credit Quality."
For comparison purposes, a summary of the changes in the allowance for loan losses by portfolio segment for the year ended December 31, 2017, was as follows.
($ in Thousands) | Commercial and industrial | Commercial real estate - owner occupied | Commercial real estate - investor | Real estate construction | Residential mortgage | Home equity | Other consumer | Total
December 31, 2016 | $ | 140,126 |  | $ | 14,034 |  | $ | 45,285 |  | $ | 26,932 |  | $ | 27,046 |  | $ | 20,364 |  | $ | 4,548 |  | $ | 278,335 |
Charge offs | (44,533 | ) | (344 | ) | (991 | ) | (604 | ) | (2,611 | ) | (2,724 | ) | (4,439 | ) | (56,246 | )
Recoveries | 11,465 |  | 173 |  | 242 |  | 74 |  | 927 |  | 3,194 |  | 716 |  | 16,791 |
Net Charge offs | (33,068 | ) | (171 | ) | (749 | ) | (530 | ) | (1,684 | ) | 470 |  | (3,723 | ) | (39,455 | )
Provision for loan losses | 16,010 |  | (3,511 | ) | (3,477 | ) | 7,968 |  | 4,245 |  | 1,292 |  | 4,473 |  | 27,000 |
December 31, 2017 | $ | 123,068 |  | $ | 10,352 |  | $ | 41,059 |  | $ | 34,370 |  | $ | 29,607 |  | $ | 22,126 |  | $ | 5,298 |  | $ | 265,880 |
Allowance for loan losses |  |  |  |  |  |  |  |
Individually evaluated for impairment | $ | 10,838 |  | $ | 2,973 |  | $ | 1,597 |  | $ | 86 |  | $ | 6,512 |  | $ | 3,718 |  | $ | 122 |  | $ | 25,846 |
Collectively evaluated for impairment | 112,230 |  | 7,379 |  | 39,462 |  | 34,284 |  | 23,095 |  | 18,408 |  | 5,176 |  | 240,034 |
Total allowance for loan losses | $ | 123,068 |  | $ | 10,352 |  | $ | 41,059 |  | $ | 34,370 |  | $ | 29,607 |  | $ | 22,126 |  | $ | 5,298 |  | $ | 265,880 |
Loans |  |  |  |  |  |  |  |
Individually evaluated for impairment | $ | 142,244 |  | $ | 26,234 |  | $ | 19,118 |  | $ | 467 |  | $ | 47,486 |  | $ | 10,891 |  | $ | 1,135 |  | $ | 247,575 |
Collectively evaluated for impairment | 6,257,449 |  | 775,975 |  | 3,296,136 |  | 1,451,217 |  | 7,499,048 |  | 872,913 |  | 384,678 |  | 20,537,416 |
Total loans | $ | 6,399,693 |  | $ | 802,209 |  | $ | 3,315,254 |  | $ | 1,451,684 |  | $ | 7,546,534 |  | $ | 883,804 |  | $ | 385,813 |  | $ | 20,784,991 |
The allowance related to the oil and gas portfolio was $17 million at June 30, 2018 and represented 2.5% of total oil and gas loans.
($ in Millions) | Six Months Ended June 30, 2018 |  | Year Ended December 31, 2017
Balance at beginning of period | $ | 27 |  |  | $ | 38 |
Charge offs | (14 | ) |  | (25 | )
Recoveries | 3 |  |  | — |
Net Charge offs | (11 | ) |  | (25 | )
Provision for loan losses | 1 |  |  | 14 |
Balance at end of period | $ | 17 |  |  | $ | 27 |
Allowance for loan losses |  |  |
Individually evaluated for impairment | $ | 9 |  |  | $ | 5 |
Collectively evaluated for impairment | 8 |  |  | 22 |
Total allowance for loan losses | $ | 17 |  |  | $ | 27 |
Loans |  |  |
Individually evaluated for impairment | $ | 45 |  |  | $ | 77 |
Collectively evaluated for impairment | 637 |  |  | 523 |
Total loans | $ | 682 |  |  | $ | 600 |
The following table presents a summary of the changes in the allowance for unfunded commitments.
| Six Months Ended June 30, 2018 |  | Year Ended December 31, 2017
| ($ in Thousands)
Allowance for Unfunded Commitments |  |  |
Balance at beginning of period | $ | 24,400 |  |  | $ | 25,400 |
Provision for unfunded commitments | (500 | ) |  | (1,000 | )
Amount recorded at acquisition | 2,436 |  |  | — |
Balance at end of period | $ | 26,336 |  |  | $ | 24,400 |
Loans Acquired in Acquisition Loans acquired in a business combination are recorded at estimated fair value on their purchase date without a carryover of the related allowance for loan and lease losses. Acquired loans are segregated into two types:
• | Performing loans are accounted for in accordance with ASC Topic 310-20 "Nonrefundable Fees and Other Costs" as these loans do not have evidence of credit deterioration since origination.
• | Nonperforming loans are accounted for in accordance with ASC Topic 310-30 as they display significant credit deterioration since origination.
For performing loans the difference between the estimated fair value of the loans and the principal outstanding is accreted over the remaining life of the loans. In accordance with ASC 310-30, purchased credit-impaired loans are pooled by loan type and the difference between contractually required payments at acquisition and the cash flows expected to be collected is referred to as the non-accretable difference. Further, any excess of cash flows expected at acquisition over the estimated fair value is referred to as the accretable yield and is recognized into interest income over the remaining life of the loan pools when there is a reasonable expectation about the amount and timing of such cash flows. If a reasonable expectation on the amount or timing of such cash flows cannot be determined, accretion of the fair value discount for nonperforming loans will be recognized using the cost recovery method of accounting. Changes in the accretable yield for loans acquired and accounted for under ASC Topic 310-30 were as follows for the six months ended June 30, 2018 and for the year ended December 31, 2017
| Six Months Ended June 30, 2018 |  | Year Ended December 31, 2017
| ($ in Thousands)
Changes in Accretable Yield |  |  |
Balance at beginning of period | $ | — |  |  | $ | — |
Purchases | 4,881 |  |  | — |
Accretion | (119 | ) |  | — |
Balance at end of period | $ | 4,762 |  |  | $ | — |
For loans acquired, the fair value of purchased credit-impaired loans, on the acquisition date, was determined based on assigned risk ratings, expected cash flows and the fair value of loan collateral. The fair value of loans that were non-impaired was determined based on estimates of losses on defaults and other market factors. At June 30, 2018, the Corporation had a total of approximately $32 million in net unaccreted purchase discount, of which approximately $26 million was related to performing loans and approximately $7 million was related to nonperforming loans.

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