Loans and Allowance - Allowance for Credit Losses and Loan Portfolio by Loan Segment (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance balances - Individually evaluated for impairment	$ 2,735		$ 2,119
Allowance balances - Collectively evaluated for impairment	59,462		61,195
Total Allowance for Loan Losses	62,550	$ 62,801	63,964	$ 68,367	$ 69,583	$ 67,870
Loan balances - Individually evaluated for impairment	35,034		44,093
Loan balances - Collectively evaluated for impairment	4,135,585		3,807,707
Loans	4,238,205		3,924,865
Loans Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for Loan Losses	353		650
Loans	67,586		73,065
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance balances - Individually evaluated for impairment	2,058		1,455
Allowance balances - Collectively evaluated for impairment	29,421		27,369
Total Allowance for Loan Losses	31,479	30,007	28,824	28,614	30,907	27,176
Loan balances - Individually evaluated for impairment	8,077		16,108
Loan balances - Collectively evaluated for impairment	1,205,104		1,011,122
Loans	$ 1,220,924		$ 1,036,633
Commercial | Loans Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for Loan Losses
Loans	$ 7,743		$ 9,403
Commercial Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance balances - Individually evaluated for impairment	328		470
Allowance balances - Collectively evaluated for impairment	15,340		18,207
Total Allowance for Loan Losses	15,828	16,383	19,327	22,582	22,358	23,102
Loan balances - Individually evaluated for impairment	21,945		23,963
Loan balances - Collectively evaluated for impairment	1,885,287		1,796,797
Loans	1,961,730		1,879,882
Commercial Real Estate | Loans Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for Loan Losses	160		650
Loans	$ 54,498		59,122
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance balances - Individually evaluated for impairment
Allowance balances - Collectively evaluated for impairment	$ 2,927		2,658
Total Allowance for Loan Losses	2,927	3,138	2,658	2,243	2,410	2,515
Loan balances - Collectively evaluated for impairment	62,785		73,400
Loans	$ 62,785		$ 73,400
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	$ 349		$ 194
Allowance balances - Collectively evaluated for impairment	11,769		12,958
Total Allowance for Loan Losses	12,311	13,269	13,152	$ 14,928	$ 13,908	$ 15,077
Loan balances - Individually evaluated for impairment	5,012		4,022
Loan balances - Collectively evaluated for impairment	981,667		925,282
Loans	992,024		$ 933,844
Residential | Loans Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for Loan Losses	193
Loans	5,345		$ 4,540
Finance Leases
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance balances - Collectively evaluated for impairment	5		3
Total Allowance for Loan Losses	5	$ 4	3
Loan balances - Collectively evaluated for impairment	742		1,106
Loans	$ 742		$ 1,106
Finance Leases | Loans Acquired with Deteriorated Credit Quality
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Allowance for Loan Losses
Loans