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Loans, Allowance for Loan Losses and Credit Quality (Internal Risk-Rating Categories for the Commercial Portfolio) (Details) - USD ($) | 3 Months Ended |
--- | --- | ---
Jun. 30, 2019 | Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Line Items] |  |
Significant Advanced Considered For Risk Rating Change | $ 50,000 |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 6,124,515,000 | $ 4,874,718,000
Commercial and Industrial [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 1,400,924,000 | 1,093,629,000
Commercial Real Estate [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 4,058,066,000 | 3,251,248,000
Commercial Construction [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 491,598,000 | 365,165,000
Small Business [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 173,927,000 | 164,676,000
PASS [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 5,854,066,000 | 4,695,094,000
PASS [Member] | Commercial and Industrial [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 1,279,778,000 | 1,014,370,000
PASS [Member] | Commercial Real Estate [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 3,917,266,000 | 3,156,989,000
PASS [Member] | Commercial Construction [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 486,775,000 | 361,884,000
PASS [Member] | Small Business [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 170,247,000 | 161,851,000
POTENTIAL WEAKNESS [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 169,004,000 | 74,886,000
POTENTIAL WEAKNESS [Member] | Commercial and Industrial [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 61,051,000 | 16,860,000
POTENTIAL WEAKNESS [Member] | Commercial Real Estate [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 103,537,000 | 56,840,000
POTENTIAL WEAKNESS [Member] | Commercial Construction [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 2,883,000 | 298,000
POTENTIAL WEAKNESS [Member] | Small Business [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 1,533,000 | 888,000
DEFINITE WEAKNESS-LOSS UNLIKELY [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 101,445,000 | 101,248,000
DEFINITE WEAKNESS-LOSS UNLIKELY [Member] | Commercial and Industrial [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 60,095,000 | 58,909,000
DEFINITE WEAKNESS-LOSS UNLIKELY [Member] | Commercial Real Estate [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 37,263,000 | 37,419,000
DEFINITE WEAKNESS-LOSS UNLIKELY [Member] | Commercial Construction [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 1,940,000 | 2,983,000
DEFINITE WEAKNESS-LOSS UNLIKELY [Member] | Small Business [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 2,147,000 | 1,937,000
PARTIAL LOSS PROBABLE [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 0 | 3,490,000
PARTIAL LOSS PROBABLE [Member] | Commercial and Industrial [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 0 | 3,490,000
PARTIAL LOSS PROBABLE [Member] | Commercial Real Estate [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 0 | 0
PARTIAL LOSS PROBABLE [Member] | Commercial Construction [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 0 | 0
PARTIAL LOSS PROBABLE [Member] | Small Business [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 0 | 0
DEFINITE LOSS [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 0 | 0
DEFINITE LOSS [Member] | Commercial and Industrial [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 0 | 0
DEFINITE LOSS [Member] | Commercial Real Estate [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 0 | 0
DEFINITE LOSS [Member] | Commercial Construction [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 0 | 0
DEFINITE LOSS [Member] | Small Business [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | $ 0 | $ 0

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