Loans and Allowance - Changes in Allowance for Loan Losses by Loan Segment (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Allowance for loan losses:
Beginning balance	$ 69,583	$ 68,537	$ 67,870	$ 69,366
Provision for losses		1,997		4,099
Recoveries on loans	1,205	2,526	4,805	6,272
Loans charged off	(2,421)	(4,858)	(4,308)	(11,535)
Ending balance	68,367	68,202	68,367	68,202
Commercial
Allowance for loan losses:
Beginning balance	30,907	25,371	27,176	25,913
Provision for losses	(2,036)	1,917	351	2,275
Recoveries on loans	448	683	2,498	2,556
Loans charged off	(705)	(1,408)	(1,411)	(4,181)
Ending balance	28,614	26,563	28,614	26,563
Commercial Real Estate
Allowance for loan losses:
Beginning balance	22,358	24,978	23,102	26,703
Provision for losses	552	(673)	(705)	(1,428)
Recoveries on loans	351	1,389	1,141	2,765
Loans charged off	(679)	(2,089)	(956)	(4,435)
Ending balance	22,582	23,605	22,582	23,605
Consumer
Allowance for loan losses:
Beginning balance	2,410	2,689	2,515	2,593
Provision for losses	(140)	225	(152)	298
Recoveries on loans	81	107	217	316
Loans charged off	(108)	(136)	(337)	(322)
Ending balance	2,243	2,885	2,243	2,885
Residential
Allowance for loan losses:
Beginning balance	13,908	15,479	15,077	14,157
Provision for losses	1,622	497	524	2,903
Recoveries on loans	325	347	929	635
Loans charged off	(927)	(1,210)	(1,602)	(2,582)
Ending balance	14,928	15,113	14,928	15,113
Finance Leases
Allowance for loan losses:
Beginning balance		20
Provision for losses	2	31	(18)	51
Recoveries on loans			20
Loans charged off	(2)	(15)	(2)	(15)
Ending balance		$ 36		$ 36