Allowance Allocations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				$ 55,100				$ 53,239	$ 55,100	$ 53,239	$ 51,834
Charge-offs									(4,918)	(10,947)	(10,518)
Recoveries									4,143	2,405	1,723
Provision (benefit)	$ 500	$ 800	$ 700	(500)	$ 1,750	$ 1,901	$ 2,250	4,502	1,500	10,403	10,200
Ending balance	55,825				55,100				55,825	55,100	53,239
Ending balance: individually evaluated for impairment	1,930				2,416				1,930	2,416	3,774
Ending balance: collectively evaluated for impairment	53,895				52,684				53,895	52,684	49,465
Financing receivables ending balance:
Financing Receivable, Collectively Evaluated for Impairment	5,475,716				4,890,383				5,475,716	4,890,383	4,616,708
Individually evaluated for impairment	51,410				58,035				51,410	58,035	72,055
Financing Receivable, Net	3,966,324				3,559,403				3,966,324	3,559,403
Loans Receivable, Gross, Commercial and Industrial	843,276				860,839				843,276	860,839
Loans Receivable, Gross, Commercial, Mortgage	2,653,434				2,347,323				2,653,434	2,347,323
Total loans	5,547,721				4,970,733				5,547,721	4,970,733	4,718,307	[1]
Loans and Leases Receivable, Gross, Consumer, Other	14,988				17,208				14,988	17,208
Loans Receivable, Gross, Commercial, Construction	373,368				265,994				373,368	265,994
Small Business	96,246				85,247				96,246	85,247
Loans and Leases Receivable, Gross, Consumer, Mortgage	638,606				530,259				638,606	530,259
Commercial and Industrial [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				15,573				15,622	15,573	15,622	13,461
Charge-offs									(2,010)	(2,097)	(2,683)
Recoveries									1,593	462	272
Provision (benefit)									(1,354)	1,586	4,572
Ending balance	13,802				15,573				13,802	15,573	15,622
Ending balance: individually evaluated for impairment	183				412				183	412	1,150
Ending balance: collectively evaluated for impairment	13,619				15,161				13,619	15,161	14,472
Financing receivables ending balance:
Financing Receivable, Collectively Evaluated for Impairment	838,129				856,185				838,129	856,185	775,053
Individually evaluated for impairment	5,147				4,654				5,147	4,654	9,148
Financing Receivable, Net	843,276				860,839				843,276	860,839
Total loans	843,276				860,839				843,276	860,839	784,202
Commercial Real Estate [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				25,873				24,541	25,873	24,541	22,598
Charge-offs									(330)	(5,454)	(3,587)
Recoveries									1,073	404	206
Provision (benefit)									711	6,382	5,324
Ending balance	27,327				25,873				27,327	25,873	24,541
Ending balance: individually evaluated for impairment	204				197				204	197	765
Ending balance: collectively evaluated for impairment	27,123				25,676				27,123	25,676	23,776
Financing receivables ending balance:
Financing Receivable, Collectively Evaluated for Impairment	2,619,294				2,304,099				2,619,294	2,304,099	2,191,132
Individually evaluated for impairment	22,986				30,729				22,986	30,729	39,516
Financing Receivable, Net	2,653,434				2,347,323				2,653,434	2,347,323
Total loans	2,653,434				2,347,323				2,653,434	2,347,323	2,249,260
Construction Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				3,945				3,371	3,945	3,371	2,811
Charge-offs									0	0	(308)
Recoveries									0	0	100
Provision (benefit)									1,421	574	768
Ending balance	5,366				3,945				5,366	3,945	3,371
Ending balance: individually evaluated for impairment	0				0				0	0	0
Ending balance: collectively evaluated for impairment	5,366				3,945				5,366	3,945	3,371
Financing receivables ending balance:
Financing Receivable, Collectively Evaluated for Impairment	373,064				265,501				373,064	265,501	223,562
Individually evaluated for impairment	304				311				304	311	100
Financing Receivable, Net	373,368				265,994				373,368	265,994
Total loans	373,368				265,994				373,368	265,994	223,859
Small Business [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				1,171				1,215	1,171	1,215	1,524
Charge-offs									(267)	(605)	(773)
Recoveries									264	275	279
Provision (benefit)									96	286	185
Ending balance	1,264				1,171				1,264	1,171	1,215
Ending balance: individually evaluated for impairment	4				7				4	7	109
Ending balance: collectively evaluated for impairment	1,260				1,164				1,260	1,164	1,106
Financing receivables ending balance:
Financing Receivable, Collectively Evaluated for Impairment	95,225				84,159				95,225	84,159	75,337
Individually evaluated for impairment	1,021				1,088				1,021	1,088	1,903
Financing Receivable, Net	96,246				85,247				96,246	85,247
Total loans	96,246				85,247				96,246	85,247	77,240
Residential Real Estate [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				2,834				2,760	2,834	2,760	2,930
Charge-offs									(285)	(826)	(622)
Recoveries									133	424	143
Provision (benefit)									(92)	476	309
Ending balance	2,590				2,834				2,590	2,834	2,760
Ending balance: individually evaluated for impairment	1,278				1,500				1,278	1,500	1,564
Ending balance: collectively evaluated for impairment	1,312				1,334				1,312	1,334	1,196
Financing receivables ending balance:
Financing Receivable, Collectively Evaluated for Impairment	614,014				505,799				614,014	505,799	515,854
Individually evaluated for impairment	15,405				15,055				15,405	15,055	15,200
Total loans	638,606				530,259				638,606	530,259	541,443
Home Equity [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				4,956				5,036	4,956	5,036	7,703
Charge-offs									(710)	(750)	(1,370)
Recoveries									356	249	135
Provision (benefit)									287	421	(1,432)
Ending balance	4,889				4,956				4,889	4,956	5,036
Ending balance: individually evaluated for impairment	238				262				238	262	116
Ending balance: collectively evaluated for impairment	4,651				4,694				4,651	4,694	4,920
Financing receivables ending balance:
Financing Receivable, Collectively Evaluated for Impairment	921,563				858,305				921,563	858,305	816,925
Individually evaluated for impairment	5,989				5,330				5,989	5,330	4,890
Total loans	927,803				863,863				927,803	863,863	822,141
Consumer Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance				$ 748				$ 694	748	694	807
Charge-offs									(1,316)	(1,215)	(1,175)
Recoveries									724	591	588
Provision (benefit)									431	678	474
Ending balance	587				748				587	748	694
Ending balance: individually evaluated for impairment	23				38				23	38	70
Ending balance: collectively evaluated for impairment	564				710				564	710	624
Financing receivables ending balance:
Financing Receivable, Collectively Evaluated for Impairment	14,427				16,335				14,427	16,335	18,845
Individually evaluated for impairment	558				868				558	868	1,298
Total loans					17,208					17,208	20,162
Receivables Acquired with Deteriorated Credit Quality [Member]
Financing receivables ending balance:
Financing Receivable, Net	20,595				22,315				20,595	22,315	29,544
Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial and Industrial [Member]
Financing receivables ending balance:
Financing Receivable, Net	0				0				0	0	1
Receivables Acquired with Deteriorated Credit Quality [Member] | Commercial Real Estate [Member]
Financing receivables ending balance:
Financing Receivable, Net	11,154				12,495				11,154	12,495	18,612
Receivables Acquired with Deteriorated Credit Quality [Member] | Construction Loans [Member]
Financing receivables ending balance:
Financing Receivable, Net	0				182				0	182	197
Receivables Acquired with Deteriorated Credit Quality [Member] | Small Business [Member]
Financing receivables ending balance:
Financing Receivable, Net	0				0				0	0	0
Receivables Acquired with Deteriorated Credit Quality [Member] | Residential Real Estate [Member]
Financing receivables ending balance:
Financing Receivable, Net	9,187				9,405				9,187	9,405	10,389
Receivables Acquired with Deteriorated Credit Quality [Member] | Home Equity [Member]
Financing receivables ending balance:
Financing Receivable, Net	251				228				251	228	326
Receivables Acquired with Deteriorated Credit Quality [Member] | Consumer Portfolio Segment [Member]
Financing receivables ending balance:
Financing Receivable, Net	$ 3				$ 5				$ 3	$ 5	$ 19

[1] The amount of net deferred fees on loans and net unamortized discounts on acquired loans not deemed to be PCI included in the ending balance was $10.9 million, $4.7 million, and $3.9 million at December 31, 2015, 2014, and 2013, respectively.