Loans and Allowance - Changes in Allowance for Loan Losses by Loan Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Allowance for loan losses:
Beginning balance	$ 62,801	$ 69,583	$ 63,964	$ 67,870
Provision for losses	417	0	417	0
Recoveries on loans	1,432	1,205	2,504	4,805
Loans charged off	(2,100)	(2,421)	(4,335)	(4,308)
Ending balance	62,550	68,367	62,550	68,367
Commercial
Allowance for loan losses:
Beginning balance	30,007	30,907	28,824	27,176
Provision for losses	1,190	(2,036)	3,024	351
Recoveries on loans	437	448	887	2,498
Loans charged off	(155)	(705)	(1,256)	(1,411)
Ending balance	31,479	28,614	31,479	28,614
Commercial Real Estate
Allowance for loan losses:
Beginning balance	16,383	22,358	19,327	23,102
Provision for losses	(502)	552	(3,398)	(705)
Recoveries on loans	147	351	559	1,141
Loans charged off	(200)	(679)	(660)	(956)
Ending balance	15,828	22,582	15,828	22,582
Consumer
Allowance for loan losses:
Beginning balance	3,138	2,410	2,658	2,515
Provision for losses	(200)	(140)	327	(152)
Recoveries on loans	101	81	179	217
Loans charged off	(112)	(108)	(237)	(337)
Ending balance	2,927	2,243	2,927	2,243
Residential
Allowance for loan losses:
Beginning balance	13,269	13,908	13,152	15,077
Provision for losses	(72)	1,622	462	524
Recoveries on loans	747	325	879	929
Loans charged off	(1,633)	(927)	(2,182)	(1,602)
Ending balance	12,311	$ 14,928	12,311	$ 14,928
Finance Leases
Allowance for loan losses:
Beginning balance	4		3
Provision for losses	$ 1	$ 2	$ 2	$ (18)
Recoveries on loans				20
Loans charged off		$ (2)		$ (2)
Ending balance	$ 5		$ 5