Allowance Allocations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended										12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance					$ 53,239					$ 51,834	$ 53,239		$ 51,834		$ 48,260
Charge-offs											(10,947)		(10,518)		(16,592)
Recoveries											2,405		1,723		2,110
Provision	1,750		1,901	2,250	4,502	3,150		2,650	3,100	1,300	10,403		10,200		18,056
Ending balance	55,100					53,239					55,100		53,239		51,834
Ending balance: individually evaluated for impairment	2,416					3,774					2,416		3,774		3,420
Ending balance: collectively evaluated for impairment	52,684					49,465					52,684		49,465		48,414
Financing receivables ending balance:
Collectively evaluated for impairment	4,890,383					4,616,708					4,890,383		4,616,708		4,420,298
Individually evaluated for impairment	58,035					72,055					58,035		72,055		66,659
Purchase credit impaired loans	22,315					29,544					22,315		29,544		32,054
Total loans	4,970,733	[1]				4,718,307	[1]				4,970,733	[1]	4,718,307	[1]	4,519,011	[1]
Commercial and Industrial [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance					15,622					13,461	15,622		13,461		11,682
Charge-offs											(2,097)		(2,683)		(6,191)
Recoveries											462		272		963
Provision											1,586		4,572		7,007
Ending balance	15,573					15,622					15,573		15,622		13,461
Ending balance: individually evaluated for impairment	412					1,150					412		1,150		1,084
Ending balance: collectively evaluated for impairment	15,161					14,472					15,161		14,472		12,377
Financing receivables ending balance:
Collectively evaluated for impairment	856,185					775,053					856,185		775,053		678,936
Individually evaluated for impairment	4,654					9,148					4,654		9,148		8,575
Purchase credit impaired loans	0					1					0		1		0
Total loans	860,839					784,202					860,839		784,202		687,511
Commercial Real Estate [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance					24,541					22,598	24,541		22,598		23,514
Charge-offs											(5,454)		(3,587)		(4,348)
Recoveries											404		206		188
Provision											6,382		5,324		3,244
Ending balance	25,873					24,541					25,873		24,541		22,598
Ending balance: individually evaluated for impairment	197					765					197		765		516
Ending balance: collectively evaluated for impairment	25,676					23,776					25,676		23,776		22,082
Financing receivables ending balance:
Collectively evaluated for impairment	2,304,099					2,191,132					2,304,099		2,191,132		2,066,432
Individually evaluated for impairment	30,729					39,516					30,729		39,516		33,868
Purchase credit impaired loans	12,495					18,612					12,495		18,612		21,853
Total loans	2,347,323					2,249,260					2,347,323		2,249,260		2,122,153
Commercial Construction [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance					3,371					2,811	3,371		2,811		2,076
Charge-offs													(308)
Recoveries													100
Provision											574		768		735
Ending balance	3,945					3,371					3,945		3,371		2,811
Ending balance: collectively evaluated for impairment	3,945					3,371					3,945		3,371		2,811
Financing receivables ending balance:
Collectively evaluated for impairment	265,501					223,562					265,501		223,562		188,768
Individually evaluated for impairment	311					100					311		100
Purchase credit impaired loans	182					197					182		197		0
Total loans	265,994					223,859					265,994		223,859		188,768
Small Business [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance					1,215					1,524	1,215		1,524		1,896
Charge-offs											(605)		(773)		(616)
Recoveries											275		279		134
Provision											286		185		110
Ending balance	1,171					1,215					1,171		1,215		1,524
Ending balance: individually evaluated for impairment	7					109					7		109		353
Ending balance: collectively evaluated for impairment	1,164					1,106					1,164		1,106		1,171
Financing receivables ending balance:
Collectively evaluated for impairment	84,159					75,337					84,159		75,337		76,315
Individually evaluated for impairment	1,088					1,903					1,088		1,903		2,279
Purchase credit impaired loans	0					0					0		0		0
Total loans	85,247					77,240					85,247		77,240		78,594
Residential Real Estate [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance					2,760					2,930	2,760		2,930		3,113
Charge-offs											(826)		(622)		(1,094)
Recoveries											424		143		151
Provision											476		309		760
Ending balance	2,834					2,760					2,834		2,760		2,930
Ending balance: individually evaluated for impairment	1,500					1,564					1,500		1,564		1,302
Ending balance: collectively evaluated for impairment	1,334					1,196					1,334		1,196		1,628
Financing receivables ending balance:
Collectively evaluated for impairment	505,799					515,854					505,799		515,854		587,687
Individually evaluated for impairment	15,055					15,200					15,055		15,200		15,373
Purchase credit impaired loans	9,405					10,389					9,405		10,389		9,821
Total loans	530,259					541,443					530,259		541,443		612,881
Home Equity [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance					5,036					7,703	5,036		7,703		4,597
Charge-offs											(750)		(1,370)		(3,178)
Recoveries											249		135		93
Provision											421		(1,432)		6,191
Ending balance	4,956					5,036					4,956		5,036		7,703
Ending balance: individually evaluated for impairment	262					116					262		116		35
Ending balance: collectively evaluated for impairment	4,694					4,920					4,694		4,920		7,668
Financing receivables ending balance:
Collectively evaluated for impairment	858,305					816,925					858,305		816,925		797,334
Individually evaluated for impairment	5,330					4,890					5,330		4,890		4,435
Purchase credit impaired loans	228					326					228		326		380
Total loans	863,863					822,141					863,863		822,141		802,149
Consumer Other [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance					694					807	694		807		1,382
Charge-offs											(1,215)		(1,175)		(1,165)
Recoveries											591		588		581
Provision											678		474		9
Ending balance	748					694					748		694		807
Ending balance: individually evaluated for impairment	38					70					38		70		130
Ending balance: collectively evaluated for impairment	710					624					710		624		677
Financing receivables ending balance:
Collectively evaluated for impairment	16,335					18,845					16,335		18,845		24,826
Individually evaluated for impairment	868					1,298					868		1,298		2,129
Purchase credit impaired loans	5					19					5		19		0
Total loans	$ 17,208					$ 20,162					$ 17,208		$ 20,162		$ 26,955

[1] The amount of net deferred fees included in the ending balance was $2.8 million, $2.3 million, and $3.1 million at December 31, 2014, 2013, and 2012, respectively.