Loans and Allowance - Allowance for Credit Losses and Loan Portfolio by Loan Segment (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance balances - Individually evaluated for impairment	$ 1,918		$ 1,689
Allowance balances - Collectively evaluated for impairment	60,066		60,611
Total Allowance for Loan Losses	62,186	$ 62,086	62,453	$ 62,550	$ 62,801	$ 63,964
Loan balances - Individually evaluated for impairment	32,421		28,567
Loan balances - Collectively evaluated for impairment	4,703,203		4,595,698
Loans	4,791,429		4,693,822
Loans Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for Loan Losses	202		153
Loans	55,805		69,557
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance balances - Individually evaluated for impairment	1,573		1,277
Allowance balances - Collectively evaluated for impairment	24,748		25,201
Total Allowance for Loan Losses	26,321	26,264	26,478	31,479	30,007	28,824
Loan balances - Individually evaluated for impairment	7,841		7,877
Loan balances - Collectively evaluated for impairment	1,345,826		1,298,988
Loans	1,360,124		1,314,174
Commercial | Loans Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for Loan Losses
Loans	6,457		7,309
Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance balances - Individually evaluated for impairment	276		243
Allowance balances - Collectively evaluated for impairment	21,824		21,753
Total Allowance for Loan Losses	22,280	22,317	22,145	15,828	16,383	19,327
Loan balances - Individually evaluated for impairment	21,118		16,670
Loan balances - Collectively evaluated for impairment	2,155,077		2,096,089
Loans	2,222,683		2,169,625
Commercial Real Estate | Loans Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for Loan Losses	180		149
Loans	46,488		56,866
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance balances - Individually evaluated for impairment
Allowance balances - Collectively evaluated for impairment	2,684		2,689
Total Allowance for Loan Losses	2,684	2,647	2,689	2,927	3,138	2,658
Loan balances - Individually evaluated for impairment
Loan balances - Collectively evaluated for impairment	75,205		74,717
Loans	75,205		74,717
Consumer | Loans Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for Loan Losses
Loans
Residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance balances - Individually evaluated for impairment	69		169
Allowance balances - Collectively evaluated for impairment	10,808		10,966
Total Allowance for Loan Losses	10,899	10,856	11,139	12,311	13,269	13,152
Loan balances - Individually evaluated for impairment	3,462		4,020
Loan balances - Collectively evaluated for impairment	1,126,707		1,125,316
Loans	1,133,029		1,134,718
Residential | Loans Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for Loan Losses	22		4
Loans	2,860		5,382
Finance Leases
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance balances - Individually evaluated for impairment
Allowance balances - Collectively evaluated for impairment	2		2
Total Allowance for Loan Losses	2	$ 2	2	$ 5	$ 4	$ 3
Loan balances - Individually evaluated for impairment
Loan balances - Collectively evaluated for impairment	388		588
Loans	388		588
Finance Leases | Loans Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for Loan Losses
Loans