Loans and Allowance for Credit Losses - Balance and activity in allowance for loan losses by portfolio segment and recorded investment in loans by portfolio segment (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	$ 68,652	$ 72,787	$ 70,990	$ 73,549
Charge-Offs	(3,533)	(3,181)	(6,686)	(6,533)
Recoveries	1,803	2,203	2,818	2,993
(Release) Provision	(300)	900	(500)	2,700
Ending Balance	66,622	72,709	66,622	72,709
Loans Receivable
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	66,310	70,007	68,448	71,619
Charge-Offs	(3,533)	(3,181)	(6,686)	(6,533)
Recoveries	1,803	2,203	2,818	2,993
(Release) Provision	(327)	1,100	(327)	2,050
Ending Balance	64,253	70,129	64,253	70,129
Loans Receivable | Home equity lines of credit
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	5,995	4,321	6,042	4,574
Charge-Offs	(469)	(348)	(1,192)	(421)
Recoveries	216	26	307	40
(Release) Provision	(424)	1,480	161	1,286
Ending Balance	5,318	5,479	5,318	5,479
Loans Receivable | Indirect auto
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	1,328	1,241	1,393	1,061
Charge-Offs	(366)	(130)	(599)	(258)
Recoveries	42	8	73	21
(Release) Provision	442	292	579	587
Ending Balance	1,446	1,411	1,446	1,411
Loans Receivable | Commercial | Owner occupied commercial real estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	16,864	14,952	16,732	16,041
Charge-Offs	(610)	(363)	(1,012)	(731)
Recoveries	46	78	143	89
(Release) Provision	(1,868)	1,672	(1,431)	940
Ending Balance	14,432	16,339	14,432	16,339
Loans Receivable | Commercial | Income producing commercial real estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	6,020	9,655	8,235	10,296
Charge-Offs	(121)	(74)	(343)	(322)
Recoveries	144	350	155	357
(Release) Provision	(521)	(1,731)	(2,525)	(2,131)
Ending Balance	5,522	8,200	5,522	8,200
Loans Receivable | Commercial | Construction
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	8,938	5,335	5,583	4,747
Charge-Offs	(24)	(147)	(311)	(169)
Recoveries	2	51	2	51
(Release) Provision	22	(344)	3,664	266
Ending Balance	8,938	4,895	8,938	4,895
Loans Receivable | Commercial | Commercial & industrial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	3,153	3,442	4,442	3,255
Charge-Offs	(223)	(162)	(795)	(631)
Recoveries	615	789	904	917
(Release) Provision	(338)	659	(1,344)	1,187
Ending Balance	3,207	4,728	3,207	4,728
Loans Receivable | Residential | Residential mortgage
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	14,205	20,138	17,232	20,311
Charge-Offs	(1,060)	(1,109)	(1,236)	(1,687)
Recoveries	231	322	358	484
(Release) Provision	2,286	(299)	(692)	(56)
Ending Balance	15,662	19,052	15,662	19,052
Loans Receivable | Residential | Construction
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	9,034	10,210	7,961	10,603
Charge-Offs	(270)	(499)	(329)	(1,639)
Recoveries	278	392	441	471
(Release) Provision	(37)	(766)	932	(98)
Ending Balance	9,005	9,337	9,005	9,337
Loans Receivable | Consumer installment
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	773	713	828	731
Charge-Offs	(390)	(349)	(869)	(675)
Recoveries	229	187	435	563
(Release) Provision	111	137	329	69
Ending Balance	723	688	723	688
Loans Receivable | Allowance for unfunded commitments
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning Balance	2,342	2,780	2,542	1,930
Charge-Offs
Recoveries
(Release) Provision	27	(200)	(173)	650
Ending Balance	$ 2,369	$ 2,580	$ 2,369	$ 2,580