Loans and Allowance - Changes in Allowance for Loan Losses by Loan Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Allowance for loan losses:
Beginning balance	$ 62,086	$ 62,801	$ 62,453	$ 63,964
Provision for losses	790	417	1,340	417
Recoveries on loans	1,339	1,432	2,973	2,504
Loans charged off	(2,029)	(2,100)	(4,580)	(4,335)
Ending balance	62,186	62,550	62,186	62,550
Commercial
Allowance for loan losses:
Beginning balance	26,264	30,007	26,478	28,824
Provision for losses	400	1,190	539	3,024
Recoveries on loans	683	437	975	887
Loans charged off	(1,026)	(155)	(1,671)	(1,256)
Ending balance	26,321	31,479	26,321	31,479
Commercial Real Estate
Allowance for loan losses:
Beginning balance	22,317	16,383	22,145	19,327
Provision for losses	200	(502)	414	(3,398)
Recoveries on loans	276	147	1,228	559
Loans charged off	(513)	(200)	(1,507)	(660)
Ending balance	22,280	15,828	22,280	15,828
Consumer
Allowance for loan losses:
Beginning balance	2,647	3,138	2,689	2,658
Provision for losses	44	(200)	77	327
Recoveries on loans	107	101	185	179
Loans charged off	(114)	(112)	(267)	(237)
Ending balance	2,684	2,927	2,684	2,927
Residential
Allowance for loan losses:
Beginning balance	10,856	13,269	11,139	13,152
Provision for losses	146	(72)	310	462
Recoveries on loans	273	747	585	879
Loans charged off	(376)	(1,633)	(1,135)	(2,182)
Ending balance	10,899	12,311	10,899	12,311
Finance Leases
Allowance for loan losses:
Beginning balance	2	4	2	3
Provision for losses		1		2
Recoveries on loans
Loans charged off
Ending balance	$ 2	$ 5	$ 2	$ 5