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Fair Value Measurements and Fair Value of Financial Instruments, Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Interest Rate Swaps [Abstract]
Reclassification of net unrealized gains (losses) on cash flow hedges from AOCI to interest expense	$ 405	$ 14	$ 674	$ (36)
Financial assets [Abstract]
HTM securities	532,979		532,979		$ 481,871
Financial liabilities [Abstract]
Time deposits	864,052		864,052		806,766
Long-term debt	73,778		73,778		88,869
Junior subordinated debt	101,196		101,196		101,196
Carrying Amount [Member] | Level 2 [Member]
Financial assets [Abstract]
HTM securities	544,163		544,163		484,073
Financial liabilities [Abstract]
Time deposits	864,052		864,052		806,766
Long-term debt	73,778		73,778		88,869
Junior subordinated debt	101,196		101,196		101,196
Carrying Amount [Member] | Level 3 [Member]
Financial assets [Abstract]
Net loans	6,786,613		6,786,613		6,515,273
Estimated Fair Value [Member] | Level 2 [Member]
Financial assets [Abstract]
HTM securities	532,979		532,979		481,871
Financial liabilities [Abstract]
Time deposits	856,646		856,646		801,294
Long-term debt	72,379		72,379		88,346
Junior subordinated debt	101,248		101,248		104,593
Estimated Fair Value [Member] | Level 3 [Member]
Financial assets [Abstract]
Net loans	6,811,553		6,811,553		6,651,931
Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member] | Other Assets [Member]
Interest Rate Swaps [Abstract]
Derivative asset, notional amount	625,700		625,700		481,200
Fair value of derivative asset	18,500		18,500		200
Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member] | Other Liabilities [Member]
Interest Rate Swaps [Abstract]
Derivative liability, notional amount	625,700		625,700		481,200
Fair value of derivative liability	18,500		18,500		200
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Interest Rate Swaps [Member]
Interest Rate Swaps [Abstract]
Notional amount	225,000		225,000		250,000
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Interest Rate Swaps [Member] | Interest Expense [Member]
Interest Rate Swaps [Abstract]
Reclassification of net unrealized gains (losses) on cash flow hedges from AOCI to interest expense	500	$ 100	900	$ (100)
Amount expected to be reclassified as a reduction to interest expense for CF hedges	3,000		3,000
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member] | Interest Rate Swaps [Member] | Other Assets [Member]
Interest Rate Swaps [Abstract]
Fair value of derivative asset	$ 4,100		$ 4,100		$ 3,500

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Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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