Allowance Allocations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				$ 60,643				$ 61,566	$ 60,643	$ 61,566	$ 55,825
Charge-offs									(2,597)	(6,209)	(3,472)
Recoveries									1,472	2,336	3,138
Provision (benefit)	$ 1,200	$ 1,075	$ 2,000	500	$ 1,300	$ 0	$ 1,050	600	4,775	2,950	6,075
Ending balance	64,293				60,643				64,293	60,643	61,566
Ending balance: collectively evaluated for impairment	63,214				59,301				63,214	59,301	56,352
Ending balance: individually evaluated for impairment	1,079				1,342				1,079	1,342	5,214
Financing receivables ending balance:
Financing Receivable, Collectively Evaluated for Impairment	6,838,339				6,269,729				6,838,339	6,269,729	5,903,916
Individually evaluated for impairment	59,060				72,801				59,060	72,801	77,297
Financing Receivable, Net	4,874,718				4,539,256				4,874,718	4,539,256
Total loans	6,906,194				6,355,553				6,906,194	6,355,553	5,999,605	[1]
Commercial and Industrial [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				13,256				16,921	13,256	16,921	13,802
Charge-offs									(355)	(3,891)	(593)
Recoveries									182	615	859
Provision (benefit)									2,677	(389)	2,853
Ending balance	15,760				13,256				15,760	13,256	16,921
Ending balance: collectively evaluated for impairment	15,753				13,246				15,753	13,246	13,260
Ending balance: individually evaluated for impairment	7				10				7	10	3,661
Financing receivables ending balance:
Financing Receivable, Collectively Evaluated for Impairment	1,064,800				853,885				1,064,800	853,885	862,875
Individually evaluated for impairment	28,829				34,643				28,829	34,643	39,178
Financing Receivable, Net	1,093,629				888,528				1,093,629	888,528
Total loans	1,093,629				888,528				1,093,629	888,528	902,053
Commercial Real Estate [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				31,453				30,369	31,453	30,369	27,327
Charge-offs									(82)	(39)	(414)
Recoveries									188	385	564
Provision (benefit)									811	738	2,892
Ending balance	32,370				31,453				32,370	31,453	30,369
Ending balance: collectively evaluated for impairment	32,333				31,411				32,333	31,411	30,173
Ending balance: individually evaluated for impairment	37				42				37	42	196
Financing receivables ending balance:
Financing Receivable, Collectively Evaluated for Impairment	3,235,418				3,093,945				3,235,418	3,093,945	2,983,642
Individually evaluated for impairment	10,839				16,638				10,839	16,638	16,813
Financing Receivable, Net	3,251,248				3,116,561				3,251,248	3,116,561
Total loans	3,251,248				3,116,561				3,251,248	3,116,561	3,010,798
Construction Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				5,698				4,522	5,698	4,522	5,366
Charge-offs									0	0	0
Recoveries									0	0	0
Provision (benefit)									(540)	1,176	(844)
Ending balance	5,158				5,698				5,158	5,698	4,522
Ending balance: collectively evaluated for impairment	5,158				5,698				5,158	5,698	4,522
Ending balance: individually evaluated for impairment	0				0				0	0	0
Financing receivables ending balance:
Financing Receivable, Collectively Evaluated for Impairment	365,165				401,797				365,165	401,797	320,391
Individually evaluated for impairment	0				0				0	0	0
Financing Receivable, Net	365,165				401,797				365,165	401,797
Total loans	365,165				401,797				365,165	401,797	320,391
Small Business [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				1,577				1,502	1,577	1,502	1,264
Charge-offs									(372)	(302)	(228)
Recoveries									46	114	195
Provision (benefit)									505	263	271
Ending balance	1,756				1,577				1,756	1,577	1,502
Ending balance: collectively evaluated for impairment	1,755				1,576				1,755	1,576	1,494
Ending balance: individually evaluated for impairment	1				1				1	1	8
Financing receivables ending balance:
Financing Receivable, Collectively Evaluated for Impairment	164,135				131,667				164,135	131,667	121,855
Individually evaluated for impairment	541				703				541	703	871
Financing Receivable, Net	164,676				132,370				164,676	132,370
Total loans	164,676				132,370				164,676	132,370	122,726
Residential Real Estate [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				2,822				2,621	2,822	2,621	2,590
Charge-offs									(148)	(207)	(28)
Recoveries									12	31	299
Provision (benefit)									533	377	(240)
Ending balance	3,219				2,822				3,219	2,822	2,621
Ending balance: collectively evaluated for impairment	2,357				1,815				2,357	1,815	1,535
Ending balance: individually evaluated for impairment	862				1,007				862	1,007	1,086
Financing receivables ending balance:
Financing Receivable, Collectively Evaluated for Impairment	906,959				733,809				906,959	733,809	622,392
Individually evaluated for impairment	12,706				13,684				12,706	13,684	14,175
Total loans	923,294				754,329				923,294	754,329	644,426
Home Equity [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				5,390				5,238	5,390	5,238	4,889
Charge-offs									(293)	(276)	(602)
Recoveries									156	198	141
Provision (benefit)									355	230	810
Ending balance	5,608				5,390				5,608	5,390	5,238
Ending balance: collectively evaluated for impairment	5,444				5,125				5,444	5,125	4,996
Ending balance: individually evaluated for impairment	164				265				164	265	242
Financing receivables ending balance:
Financing Receivable, Collectively Evaluated for Impairment	1,085,961				1,045,053				1,085,961	1,045,053	982,095
Individually evaluated for impairment	5,948				6,826				5,948	6,826	5,863
Total loans	1,092,084				1,052,088				1,092,084	1,052,088	988,147
Consumer Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				$ 447				$ 393	447	393	587
Charge-offs									(1,347)	(1,494)	(1,607)
Recoveries									888	993	1,080
Provision (benefit)									434	555	333
Ending balance	422				447				422	447	393
Ending balance: collectively evaluated for impairment	414				430				414	430	372
Ending balance: individually evaluated for impairment	8				17				8	17	21
Financing receivables ending balance:
Financing Receivable, Collectively Evaluated for Impairment	15,901				9,573				15,901	9,573	10,666
Individually evaluated for impairment	197				307				197	307	397
Total loans	16,098				9,880				16,098	9,880	11,064
Financial Asset Acquired with Credit Deterioration [Member]
Financing receivables ending balance:
Financing Receivable, Net	8,795				13,023				8,795	13,023	18,392
Financial Asset Acquired with Credit Deterioration [Member] | Commercial and Industrial [Member]
Financing receivables ending balance:
Financing Receivable, Net	0				0				0	0	0
Financial Asset Acquired with Credit Deterioration [Member] | Commercial Real Estate [Member]
Financing receivables ending balance:
Financing Receivable, Net	4,991				5,978				4,991	5,978	10,343
Financial Asset Acquired with Credit Deterioration [Member] | Construction Loans [Member]
Financing receivables ending balance:
Financing Receivable, Net	0				0				0	0	0
Financial Asset Acquired with Credit Deterioration [Member] | Small Business [Member]
Financing receivables ending balance:
Financing Receivable, Net	0				0				0	0	0
Financial Asset Acquired with Credit Deterioration [Member] | Residential Real Estate [Member]
Financing receivables ending balance:
Financing Receivable, Net	3,629				6,836				3,629	6,836	7,859
Financial Asset Acquired with Credit Deterioration [Member] | Home Equity [Member]
Financing receivables ending balance:
Financing Receivable, Net	175				209				175	209	189
Financial Asset Acquired with Credit Deterioration [Member] | Consumer Portfolio Segment [Member]
Financing receivables ending balance:
Financing Receivable, Net	$ 0				$ 0				$ 0	$ 0	$ 1

[1] The amount of net deferred costs on originated loans included in the ending balance was $7.1 million, $6.1 million and $5.1 million at December 31, 2018, 2017 and 2016, respectively. Net unamortized discounts on acquired loans not deemed to be PCI included in the ending balance were $15.2 million, $9.4 million and $8.6 million at December 31, 2018, 2017 and 2016, respectively.