Fair Value Measurements Fair Value Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Assets:
Available-for-sale, fair value	$ 994,065	$ 1,149,534
Equity securities at fair value	14,228	20,794
U.S. government and agencies
Assets:
Available-for-sale, fair value	29,114	34,299
Government-sponsored entities
Assets:
Available-for-sale, fair value	207,703	302,501
Municipal bonds
Assets:
Available-for-sale, fair value	308,959	303,058
Mortgage-backed securities
Assets:
Available-for-sale, fair value	448,289	509,676
Other
Assets:
Equity securities at fair value	14,228
Fair Value, Measurements, Recurring
Assets:
Available-for-sale, fair value	994,065	1,149,534
Equity securities at fair value		20,794
Trading securities held in the rabbi trust	6,839	7,062
Liabilities:
Deferred compensation rabbi trust	6,839	7,062
Fair Value, Measurements, Recurring \| U.S. government and agencies
Assets:
Available-for-sale, fair value	29,114	34,299
Fair Value, Measurements, Recurring \| Government-sponsored entities
Assets:
Available-for-sale, fair value	207,703	302,501
Fair Value, Measurements, Recurring \| Municipal bonds
Assets:
Available-for-sale, fair value	308,959	303,058
Fair Value, Measurements, Recurring \| Mortgage-backed securities
Assets:
Available-for-sale, fair value	448,289	509,676
Fair Value, Measurements, Recurring \| Interest rate products
Assets:
Derivative Assets	21,889	18,575
Liabilities:
Derivative liabilities	22,385	18,953
Fair Value, Measurements, Recurring \| Derivatives - customer foreign exchange forwards
Assets:
Derivative Assets		2
Fair Value, Measurements, Recurring \| Derivatives - interest rate swaps
Assets:
Derivative Assets	553	555
Liabilities:
Derivative liabilities		80
Fair Value, Measurements, Recurring \| Foreign exchange contracts
Liabilities:
Derivative liabilities		2
Fair Value, Measurements, Recurring \| Risk participation agreements
Assets:
Derivative Assets	2	1
Liabilities:
Derivative liabilities	152	108
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 1
Assets:
Available-for-sale, fair value	0	34,096
Equity securities at fair value	14,228	20,794
Trading securities held in the rabbi trust	6,839	7,062
Liabilities:
Deferred compensation rabbi trust	6,839	7,062
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 1 \| U.S. government and agencies
Assets:
Available-for-sale, fair value	0	34,096
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 1 \| Government-sponsored entities
Assets:
Available-for-sale, fair value	0	0
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 1 \| Municipal bonds
Assets:
Available-for-sale, fair value	0	0
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 1 \| Mortgage-backed securities
Assets:
Available-for-sale, fair value	0	0
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 1 \| Interest rate products
Assets:
Derivative Assets	0	0
Liabilities:
Derivative liabilities	0	0
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 1 \| Derivatives - customer foreign exchange forwards
Assets:
Derivative Assets		0
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 1 \| Derivatives - interest rate swaps
Assets:
Derivative Assets	0	0
Liabilities:
Derivative liabilities		0
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 1 \| Foreign exchange contracts
Liabilities:
Derivative liabilities		0
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 1 \| Risk participation agreements
Assets:
Derivative Assets	0	0
Liabilities:
Derivative liabilities	0	0
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2
Assets:
Available-for-sale, fair value	994,065	1,115,438
Equity securities at fair value	0	0
Trading securities held in the rabbi trust	0	0
Liabilities:
Deferred compensation rabbi trust	0	0
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2 \| U.S. government and agencies
Assets:
Available-for-sale, fair value	29,114	203
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2 \| Government-sponsored entities
Assets:
Available-for-sale, fair value	207,703	302,501
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2 \| Municipal bonds
Assets:
Available-for-sale, fair value	308,959	303,058
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2 \| Mortgage-backed securities
Assets:
Available-for-sale, fair value	448,289	509,676
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2 \| Interest rate products
Assets:
Derivative Assets	21,889	18,575
Liabilities:
Derivative liabilities	22,385	18,953
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2 \| Derivatives - customer foreign exchange forwards
Assets:
Derivative Assets		2
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2 \| Derivatives - interest rate swaps
Assets:
Derivative Assets	553	555
Liabilities:
Derivative liabilities		80
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2 \| Foreign exchange contracts
Liabilities:
Derivative liabilities		2
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2 \| Risk participation agreements
Assets:
Derivative Assets	2	1
Liabilities:
Derivative liabilities	152	108
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 3
Assets:
Available-for-sale, fair value	0	0
Equity securities at fair value	0	0
Trading securities held in the rabbi trust	0	0
Liabilities:
Deferred compensation rabbi trust	0	0
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 3 \| U.S. government and agencies
Assets:
Available-for-sale, fair value	0	0
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 3 \| Government-sponsored entities
Assets:
Available-for-sale, fair value	0	0
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 3 \| Municipal bonds
Assets:
Available-for-sale, fair value	0	0
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 3 \| Mortgage-backed securities
Assets:
Available-for-sale, fair value	0	0
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 3 \| Interest rate products
Assets:
Derivative Assets	0	0
Liabilities:
Derivative liabilities	0	0
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 3 \| Derivatives - customer foreign exchange forwards
Assets:
Derivative Assets		0
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 3 \| Derivatives - interest rate swaps
Assets:
Derivative Assets	0	0
Liabilities:
Derivative liabilities		0
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 3 \| Foreign exchange contracts
Liabilities:
Derivative liabilities		0
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 3 \| Risk participation agreements
Assets:
Derivative Assets	0	0
Liabilities:
Derivative liabilities	$ 0	$ 0

Fair value of investment other than investment in equity security, investment in debt security and equity method investment. Includes, but is not limited to, investment in certain entities that calculate net asset value per share. Example includes, but is not limited to, investment in hedge fund, venture capital fund, private equity fund, and real estate partnership or fund.

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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 of financial and nonfinancial obligations.

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