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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		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Interest Rate Swaps [Abstract]
Reclassification of net unrealized gains (losses) on cash flow hedges from AOCI to interest expense	$ 479	$ 96	$ 1,153	$ 59
Financial assets [Abstract]
HTM securities	645,732		645,732		$ 481,871
Financial liabilities [Abstract]
Time deposits	868,569		868,569		806,766
Long-term debt	73,751		73,751		88,869
Junior subordinated debt	101,196		101,196		101,196
Carrying Amount [Member] \| Level 2 [Member]
Financial assets [Abstract]
HTM securities	659,949		659,949		484,073
Financial liabilities [Abstract]
Time deposits	868,569		868,569		806,766
Long-term debt	73,751		73,751		88,869
Junior subordinated debt	101,196		101,196		101,196
Carrying Amount [Member] \| Level 3 [Member]
Financial assets [Abstract]
Net loans	6,819,492		6,819,492		6,515,273
Estimated Fair Value [Member] \| Level 2 [Member]
Financial assets [Abstract]
HTM securities	645,732		645,732		481,871
Financial liabilities [Abstract]
Time deposits	860,791		860,791		801,294
Long-term debt	72,152		72,152		88,346
Junior subordinated debt	102,979		102,979		104,593
Estimated Fair Value [Member] \| Level 3 [Member]
Financial assets [Abstract]
Net loans	6,762,901		6,762,901		6,651,931
Not Designated as Hedging Instrument [Member] \| Interest Rate Swaps [Member] \| Other Assets [Member]
Interest Rate Swaps [Abstract]
Derivative asset, notional amount	630,200		630,200		481,200
Fair value of derivative asset	20,000		20,000		200
Not Designated as Hedging Instrument [Member] \| Interest Rate Swaps [Member] \| Other Liabilities [Member]
Interest Rate Swaps [Abstract]
Derivative liability, notional amount	630,200		630,200		481,200
Fair value of derivative liability	20,000		20,000		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	600	$ 200	1,500	$ 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	$ 3,600		$ 3,600		$ 3,500