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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 |
--- | --- | ---
Sep. 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 | 6,104,626,000 | $ 4,874,718,000
Commercial and Industrial [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 1,411,516,000 | 1,093,629,000
Commercial Real Estate [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 4,000,487,000 | 3,251,248,000
Commercial Construction [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 520,585,000 | 365,165,000
Small Business [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 172,038,000 | 164,676,000
PASS [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 5,840,777,000 | 4,695,094,000
PASS [Member] | Commercial and Industrial [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 1,299,386,000 | 1,014,370,000
PASS [Member] | Commercial Real Estate [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 3,857,847,000 | 3,156,989,000
PASS [Member] | Commercial Construction [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 514,521,000 | 361,884,000
PASS [Member] | Small Business [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 169,023,000 | 161,851,000
POTENTIAL WEAKNESS [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 143,168,000 | 74,886,000
POTENTIAL WEAKNESS [Member] | Commercial and Industrial [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 47,727,000 | 16,860,000
POTENTIAL WEAKNESS [Member] | Commercial Real Estate [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 89,772,000 | 56,840,000
POTENTIAL WEAKNESS [Member] | Commercial Construction [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 4,235,000 | 298,000
POTENTIAL WEAKNESS [Member] | Small Business [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 1,434,000 | 888,000
DEFINITE WEAKNESS-LOSS UNLIKELY [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 120,681,000 | 101,248,000
DEFINITE WEAKNESS-LOSS UNLIKELY [Member] | Commercial and Industrial [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 64,403,000 | 58,909,000
DEFINITE WEAKNESS-LOSS UNLIKELY [Member] | Commercial Real Estate [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 52,868,000 | 37,419,000
DEFINITE WEAKNESS-LOSS UNLIKELY [Member] | Commercial Construction [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 1,829,000 | 2,983,000
DEFINITE WEAKNESS-LOSS UNLIKELY [Member] | Small Business [Member] |  |
Internal risk-rating categories for the Company's commercial portfolio |  |
TOTAL | 1,581,000 | 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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