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Loans (Analysis of Loan Portfolio by Major Types of Loans) (Details) - USD ($) $ in Thousands | Jun. 30, 2018 | Mar. 31, 2018 | Dec. 31, 2017 | Jun. 30, 2017 | Mar. 31, 2017 | Dec. 31, 2016
--- | --- | --- | --- | --- | --- | ---
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Less: unearned income on loans | $ (45,430) |  | $ (52,111) |  |  |
Recorded Investment | 8,454,107 |  | 8,358,657 |  |  |
Allowance for loan losses | (80,150) | $ (79,827) | (75,646) | $ (72,984) | $ (71,021) | $ (70,043)
Loans, net | 8,373,957 |  | 8,283,011 |  |  |
Loans held for sale | 6,773 |  | 5,766 |  |  |
Loans, Excluding Purchased Credit Impaired Loans [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Less: unearned income on loans | (45,430) |  | (52,111) |  |  |
Recorded Investment | 8,352,325 |  | 8,245,987 |  |  |
Allowance for loan losses | (75,368) |  | (68,739) |  |  |
Loans, net | 8,276,957 |  | 8,177,248 |  |  |
Loans held for sale | 6,773 |  | 5,766 |  |  |
Loans and Leases Receivable, Gross | 8,352,325 |  | 8,245,987 |  |  |
Purchased Credit Impaired Loans [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Less: unearned income on loans | 0 |  | 0 |  |  |
Recorded Investment | 101,782 |  | 112,670 |  |  |
Allowance for loan losses | (4,782) |  | (6,907) |  |  |
Loans, net | 97,000 |  | 105,763 |  |  |
Loans held for sale | 0 |  | 0 |  |  |
Loans and Leases Receivable, Gross | 109,175 |  | 120,758 |  |  |
Acquisition Accounting Valuation Discount on Covered Loans | 7,393 |  | 8,088 |  |  |
Commercial and Multifamily Residential Construction [Domain] | Purchased Credit Impaired Loans [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Loans and Leases Receivable, Gross | 557 |  | 595 |  |  |
One-to-Four Family Residential [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Loans and Leases Receivable, Gross, Consumer, Mortgage | 190,722 |  | 200,791 |  |  |
Loans and Leases Receivable, Gross, Consumer, Construction | 206,346 |  | 200,695 |  |  |
Allowance for loan losses | (461) | (558) | (701) | (628) | (645) | (599)
One-to-Four Family Residential [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Loans and Leases Receivable, Gross, Consumer, Mortgage | 180,522 |  | 188,396 |  |  |
Loans and Leases Receivable, Gross, Consumer, Construction | 206,181 |  | 200,518 |  |  |
Loans and Leases Receivable, Gross | 178,814 |  | 186,554 |  |  |
One-to-Four Family Residential [Member] | Purchased Credit Impaired Loans [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Loans and Leases Receivable, Gross, Consumer, Mortgage | 10,200 |  | 12,395 |  |  |
Loans and Leases Receivable, Gross, Consumer, Construction | 165 |  | 177 |  |  |
Loans and Leases Receivable, Gross | 12,202 |  | 14,610 |  |  |
Commercial and Multifamily Residential [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Loans Receivable, Gross, Commercial, Mortgage | 3,826,506 |  | 3,901,333 |  |  |
Loans Receivable, Gross, Commercial, Construction | 388,522 |  | 372,538 |  |  |
Commercial and Multifamily Residential [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Loans Receivable, Gross, Commercial, Mortgage | 3,758,207 |  | 3,825,739 |  |  |
Loans Receivable, Gross, Commercial, Construction | 387,951 |  | 371,931 |  |  |
Commercial and Multifamily Residential [Member] | Purchased Credit Impaired Loans [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Loans Receivable, Gross, Commercial, Mortgage | 68,299 |  | 75,594 |  |  |
Loans Receivable, Gross, Commercial, Construction | 571 |  | 607 |  |  |
Loans and Leases Receivable, Gross | 72,019 |  | 79,211 |  |  |
Commercial Portfolio Segment [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Loans Receivable, Gross, Commercial and Industrial | 3,550,750 |  | 3,389,952 |  |  |
Commercial Portfolio Segment [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Loans Receivable, Gross, Commercial and Industrial | 3,538,492 |  | 3,377,324 |  |  |
Commercial Portfolio Segment [Member] | Purchased Credit Impaired Loans [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Loans Receivable, Gross, Commercial and Industrial | 12,258 |  | 12,628 |  |  |
Loans and Leases Receivable, Gross | 12,921 |  | 13,753 |  |  |
Real Estate Portfolio Segment [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Loans Receivable Real Estate Mortgage | 4,017,228 |  | 4,102,124 |  |  |
Real Estate Portfolio Segment [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Loans Receivable Real Estate Mortgage | 3,938,729 |  | 4,014,135 |  |  |
Real Estate Portfolio Segment [Member] | Purchased Credit Impaired Loans [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Loans Receivable Real Estate Mortgage | 78,499 |  | 87,989 |  |  |
Loans and Leases Receivable, Gross | 84,221 |  | 93,821 |  |  |
One-to-Four Family Residential Construction [Domain] | Purchased Credit Impaired Loans [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Loans and Leases Receivable, Gross | 166 |  | 177 |  |  |
Real Estate Construction Portfolio Segment [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Loans Receivable Real Estate Construction | 594,868 |  | 573,233 |  |  |
Real Estate Construction Portfolio Segment [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Loans Receivable Real Estate Construction | 594,132 |  | 572,449 |  |  |
Real Estate Construction Portfolio Segment [Member] | Purchased Credit Impaired Loans [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Loans Receivable Real Estate Construction | 736 |  | 784 |  |  |
Loans and Leases Receivable, Gross | 723 |  | 772 |  |  |
Consumer Portfolio Segment [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Loans and Leases Receivable, Gross, Consumer | 336,691 |  | 345,459 |  |  |
Allowance for loan losses | (5,292) | $ (5,216) | (5,163) | $ (3,551) | $ (3,360) | $ (3,534)
Consumer Portfolio Segment [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Loans and Leases Receivable, Gross, Consumer | 326,402 |  | 334,190 |  |  |
Loans and Leases Receivable, Gross | 325,158 |  | 332,225 |  |  |
Consumer Portfolio Segment [Member] | Purchased Credit Impaired Loans [Member] |  |  |  |  |  |
Financing Receivable, Recorded Investment [Line Items] |  |  |  |  |  |
Loans and Leases Receivable, Gross, Consumer | 10,289 |  | 11,269 |  |  |
Loans and Leases Receivable, Gross | $ 11,310 |  | $ 12,412 |  |  |

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