Loans and Allowance - Allowance for Credit Losses and Loan Portfolio by Loan Segment (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance balances - Individually evaluated for impairment	$ 1,627		$ 1,689
Allowance balances - Collectively evaluated for impairment	61,829		60,611
Total Allowance for Loan Losses	63,456	$ 62,186	62,453	$ 62,861	$ 62,550	$ 63,964
Loan balances - Individually evaluated for impairment	33,826		28,567
Loan balances - Collectively evaluated for impairment	4,888,189		4,595,698
Loans	4,973,844		4,693,822
Loans Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for Loan Losses			153
Loans	51,829		69,557
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance balances - Individually evaluated for impairment	555		1,277
Allowance balances - Collectively evaluated for impairment	25,948		25,201
Total Allowance for Loan Losses	26,503	26,321	26,478	33,936	31,479	28,824
Loan balances - Individually evaluated for impairment	5,764		7,877
Loan balances - Collectively evaluated for impairment	1,436,065		1,298,988
Loans	1,448,295		1,314,174
Commercial | Loans Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for Loan Losses
Loans	6,466		7,309
Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance balances - Individually evaluated for impairment	760		243
Allowance balances - Collectively evaluated for impairment	22,177		21,753
Total Allowance for Loan Losses	22,937	22,280	22,145	13,986	15,828	19,327
Loan balances - Individually evaluated for impairment	23,904		16,670
Loan balances - Collectively evaluated for impairment	2,242,862		2,096,089
Loans	2,309,980		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			149
Loans	43,214		56,866
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance balances - Individually evaluated for impairment
Allowance balances - Collectively evaluated for impairment	2,786		2,689
Total Allowance for Loan Losses	2,786	2,684	2,689	2,723	2,927	2,658
Loan balances - Individually evaluated for impairment
Loan balances - Collectively evaluated for impairment	76,497		74,717
Loans	76,497		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	312		169
Allowance balances - Collectively evaluated for impairment	10,916		10,966
Total Allowance for Loan Losses	11,228	10,899	11,139	12,213	12,311	13,152
Loan balances - Individually evaluated for impairment	4,158		4,020
Loan balances - Collectively evaluated for impairment	1,132,385		1,125,316
Loans	1,138,692		1,134,718
Residential | Loans Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for Loan Losses			4
Loans	2,149		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	$ 3	$ 5	$ 3
Loan balances - Individually evaluated for impairment
Loan balances - Collectively evaluated for impairment	380		588
Loans	380		588
Finance Leases | Loans Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for Loan Losses
Loans