Loans and Allowance - Changes in Allowance for Loan Losses by Loan Segment (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Allowance for loan losses:
Beginning balance	$ 68,367	$ 68,202	$ 67,870	$ 69,366
Provision for losses	1,600	1,533	1,600	5,632
Recoveries on loans	3,722	2,176	8,527	8,448
Loans charged off	(8,093)	(5,687)	(12,401)	(17,222)
Ending balance	65,596	66,224	65,596	66,224
Commercial
Allowance for loan losses:
Beginning balance	28,614	26,563	27,176	25,913
Provision for losses	1,385	(346)	1,736	1,929
Recoveries on loans	1,987	1,494	4,485	4,050
Loans charged off	(4,444)	(1,680)	(5,855)	(5,861)
Ending balance	27,542	26,031	27,542	26,031
Commercial Real Estate
Allowance for loan losses:
Beginning balance	22,582	23,605	23,102	26,703
Provision for losses	528	1,560	(177)	132
Recoveries on loans	1,215	258	2,356	3,023
Loans charged off	(2,707)	(2,795)	(3,663)	(7,230)
Ending balance	21,618	22,628	21,618	22,628
Consumer
Allowance for loan losses:
Beginning balance	2,243	2,885	2,515	2,593
Provision for losses	113	(31)	(39)	267
Recoveries on loans	86	110	303	426
Loans charged off	(214)	(161)	(551)	(483)
Ending balance	2,228	2,803	2,228	2,803
Residential
Allowance for loan losses:
Beginning balance	14,928	15,113	15,077	14,157
Provision for losses	(424)	333	100	3,236
Recoveries on loans	431	311	1,360	946
Loans charged off	(728)	(1,051)	(2,330)	(3,633)
Ending balance	14,207	14,706	14,207	14,706
Finance Leases
Allowance for loan losses:
Beginning balance		36
Provision for losses	(2)	17	(20)	68
Recoveries on loans	3	3	23	3
Loans charged off			(2)	(15)
Ending balance	$ 1	$ 56	$ 1	$ 56