Loans and Allowance - Changes in Allowance for Loan Losses by Loan Segment (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for loan losses:
Beginning balance				$ 62,453				$ 63,964	$ 62,453	$ 63,964	$ 67,870
Provision for losses	$ 2,417	$ 1,900	$ 790	550			$ 417		5,657	417	2,560
Recoveries on loans									5,356	6,344	10,916
Loans charged off									(7,429)	(8,272)	(17,382)
Ending balance	66,037				62,453				66,037	62,453	63,964
Commercial
Allowance for loan losses:
Beginning balance				26,478				28,824	26,478	28,824	27,176
Provision for losses									1,876	(1,901)	3,459
Recoveries on loans									1,806	1,911	5,435
Loans charged off									(2,464)	(2,356)	(7,246)
Ending balance	27,696				26,478				27,696	26,478	28,824
Commercial Real Estate
Allowance for loan losses:
Beginning balance				22,145				19,327	22,145	19,327	23,102
Provision for losses									1,834	1,710	(464)
Recoveries on loans									2,090	2,545	3,297
Loans charged off									(2,408)	(1,437)	(6,608)
Ending balance	23,661				22,145				23,661	22,145	19,327
Consumer
Allowance for loan losses:
Beginning balance				2,689				2,658	2,689	2,658	2,515
Provision for losses									432	299	423
Recoveries on loans									369	352	377
Loans charged off									(567)	(620)	(657)
Ending balance	2,923				2,689				2,923	2,689	2,658
Residential
Allowance for loan losses:
Beginning balance				11,139				13,152	11,139	13,152	15,077
Provision for losses									1,515	310	(839)
Recoveries on loans									1,091	1,536	1,783
Loans charged off									(1,990)	(3,859)	(2,869)
Ending balance	11,755				11,139				11,755	11,139	13,152
Finance Leases
Allowance for loan losses:
Beginning balance				$ 2				$ 3	2	3
Provision for losses										(1)	(19)
Recoveries on loans											24
Loans charged off											(2)
Ending balance	$ 2				$ 2				$ 2	$ 2	$ 3