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Fair Value Accounting and Measurement (Carrying Amounts and Estimated Fair Values of Selected Financial Instruments) (Details) - USD ($) $ in Thousands | Mar. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Assets |  |
Interest-earning deposits with banks | $ 87,124 | $ 97,918
Available-for-sale Securities, Debt Securities | 2,624,045 | 2,737,751
Marketable Securities, Equity Securities | 5,000 | 5,080
Estimate of Fair Value Measurement [Member] |  |
Assets |  |
Cash and due from banks | 206,532 | 244,615
Interest-earning deposits with banks | 87,124 | 97,918
Available-for-sale Securities, Debt Securities | 2,624,045 | 2,737,751
Marketable Securities, Equity Securities | 5,000 | 5,080
FHLB stock | 11,640 | 10,440
Loans held for sale | 4,312 | 5,766
Loans | 8,281,010 | 8,055,817
Interest rate contracts | 7,406 | 6,707
Liabilities |  |
Deposits | 465,896 | 10,524,135
FHLB Advances | 42,090 | 12,281
Repurchase agreements | 24,247 | 79,070
Interest rate contracts | 7,409 | 6,714
Subordinated Debt Obligations, Fair Value Disclosure | 35,486 | 35,895
Junior subordinated debentures, fair value disclosure |  | 8,248
Reported Value Measurement [Member] |  |
Assets |  |
Cash and due from banks | 206,532 | 244,615
Interest-earning deposits with banks | 87,124 | 97,918
Available-for-sale Securities, Debt Securities | 2,624,045 | 2,737,751
Marketable Securities, Equity Securities | 5,000 | 5,080
FHLB stock | 11,640 | 10,440
Loans held for sale | 4,312 | 5,766
Loans | 8,259,804 | 8,283,011
Interest rate contracts | 7,406 | 6,707
Liabilities |  |
Deposits | 474,000 | 10,532,085
FHLB Advances | 41,564 | 11,579
Repurchase agreements | 24,247 | 79,059
Interest rate contracts | 7,409 | 6,714
Subordinated Debt Obligations, Fair Value Disclosure | 35,601 | 35,647
Junior subordinated debentures, fair value disclosure |  | 8,248
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member] |  |
Assets |  |
Cash and due from banks | 206,532 | 244,615
Interest-earning deposits with banks | 87,124 | 97,918
Available-for-sale Securities, Debt Securities | 247 | 248
Marketable Securities, Equity Securities | 5,000 | 5,080
FHLB stock | 0 | 0
Loans held for sale | 0 | 0
Loans | 0 | 0
Interest rate contracts | 0 | 0
Liabilities |  |
Deposits | 0 | 10,041,040
FHLB Advances | 0 | 0
Repurchase agreements | 0 | 0
Interest rate contracts | 0 | 0
Subordinated Debt Obligations, Fair Value Disclosure | 0 | 0
Junior subordinated debentures, fair value disclosure |  | 0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] |  |
Assets |  |
Cash and due from banks | 0 | 0
Interest-earning deposits with banks | 0 | 0
Available-for-sale Securities, Debt Securities | 2,623,798 | 2,737,503
Marketable Securities, Equity Securities | 0 | 0
FHLB stock | 11,640 | 10,440
Loans held for sale | 4,312 | 5,766
Loans | 0 | 0
Interest rate contracts | 7,406 | 6,707
Liabilities |  |
Deposits | 465,896 | 483,095
FHLB Advances | 42,090 | 12,281
Repurchase agreements | 24,247 | 79,070
Interest rate contracts | 7,409 | 6,714
Subordinated Debt Obligations, Fair Value Disclosure | 35,486 | 35,895
Junior subordinated debentures, fair value disclosure |  | 8,248
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member] |  |
Assets |  |
Cash and due from banks | 0 | 0
Interest-earning deposits with banks | 0 | 0
Available-for-sale Securities, Debt Securities | 0 | 0
Marketable Securities, Equity Securities | 0 | 0
FHLB stock | 0 | 0
Loans held for sale | 0 | 0
Loans | 8,281,010 | 8,055,817
Interest rate contracts | 0 | 0
Liabilities |  |
Deposits | 0 | 0
FHLB Advances | 0 | 0
Repurchase agreements | 0 | 0
Interest rate contracts | 0 | 0
Subordinated Debt Obligations, Fair Value Disclosure | $ 0 | 0
Junior subordinated debentures, fair value disclosure |  | $ 0

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- Definition Fair value portion of borrowing from Federal Home Loan Bank (FHLBank). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.13(3)(a)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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- Definition For banks and other depository institutions (including Federal Reserve Banks, if applicable): Interest-bearing deposits in other financial institutions for relatively short periods of time including, for example, certificates of deposits, which are presented separately from cash on the balance sheet. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.2) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=73530178&loc=d3e59706-112781 + Details
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