Fair Value Measurements on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financial Assets
Debt securities, available-for-sale	$ 2,522,322	$ 2,571,663
Recurring Measurements
Financial Assets
Loans held for sale, at fair value	29,389	33,156
Total assets measured at fair value on a recurring basis	2,551,711	2,604,819
Financial Liabilities
Total liabilities measured at fair value on a recurring basis	5,380	3,769
Interest Rate Swaps \| Recurring Measurements
Financial Liabilities
Derivatives	5,380	3,769
U.S. government and federal agency \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	21,521	23,649
U.S. government sponsored enterprises \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	106,457	120,208
State and local governments \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	725,191	852,250
Corporate bonds \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	218,548	290,817
Residential mortgage-backed securities \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	825,048	792,915
Commercial mortgage-backed securities \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	625,557	491,824
Level 1 \| Recurring Measurements
Financial Assets
Loans held for sale, at fair value	0	0
Total assets measured at fair value on a recurring basis	0	0
Financial Liabilities
Total liabilities measured at fair value on a recurring basis	0	0
Level 1 \| Interest Rate Swaps \| Recurring Measurements
Financial Liabilities
Derivatives	0	0
Level 1 \| U.S. government and federal agency \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 1 \| U.S. government sponsored enterprises \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 1 \| State and local governments \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 1 \| Corporate bonds \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 1 \| Residential mortgage-backed securities \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 1 \| Commercial mortgage-backed securities \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 2 \| Recurring Measurements
Financial Assets
Loans held for sale, at fair value	29,389	33,156
Total assets measured at fair value on a recurring basis	2,551,711	2,604,819
Financial Liabilities
Total liabilities measured at fair value on a recurring basis	5,380	3,769
Level 2 \| Interest Rate Swaps \| Recurring Measurements
Financial Liabilities
Derivatives	5,380	3,769
Level 2 \| U.S. government and federal agency \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	21,521	23,649
Level 2 \| U.S. government sponsored enterprises \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	106,457	120,208
Level 2 \| State and local governments \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	725,191	852,250
Level 2 \| Corporate bonds \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	218,548	290,817
Level 2 \| Residential mortgage-backed securities \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	825,048	792,915
Level 2 \| Commercial mortgage-backed securities \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	625,557	491,824
Level 3 \| Recurring Measurements
Financial Assets
Loans held for sale, at fair value	0	0
Total assets measured at fair value on a recurring basis	0	0
Financial Liabilities
Total liabilities measured at fair value on a recurring basis	0	0
Level 3 \| Interest Rate Swaps \| Recurring Measurements
Financial Liabilities
Derivatives	0	0
Level 3 \| U.S. government and federal agency \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 3 \| U.S. government sponsored enterprises \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 3 \| State and local governments \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 3 \| Corporate bonds \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 3 \| Residential mortgage-backed securities \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	0	0
Level 3 \| Commercial mortgage-backed securities \| Recurring Measurements
Financial Assets
Debt securities, available-for-sale	$ 0	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

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