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, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Allowance for loan losses:
Beginning balance	$ 68,202	$ 70,143	$ 69,366	$ 70,898
Provision for losses	1,533	4,609	5,632	14,029
Recoveries on loans	2,176	2,517	8,448	6,219
Loans charged off	(5,687)	(7,776)	(17,222)	(21,653)
Ending balance	66,224	69,493	66,224	69,493
Commercial
Allowance for loan losses:
Beginning balance	26,563	17,791	25,913	17,731
Provision for losses	(346)	5,431	1,929	10,333
Recoveries on loans	1,494	526	4,050	1,193
Loans charged off	(1,680)	(1,424)	(5,861)	(6,933)
Ending balance	26,031	22,324	26,031	22,324
Commercial Real Estate
Allowance for loan losses:
Beginning balance	23,605	35,133	26,703	37,919
Provision for losses	1,560	(879)	132	149
Recoveries on loans	258	1,598	3,023	3,462
Loans charged off	(2,795)	(4,439)	(7,230)	(10,117)
Ending balance	22,628	31,413	22,628	31,413
Consumer
Allowance for loan losses:
Beginning balance	2,885	2,431	2,593	2,902
Provision for losses	(31)	147	267	(14)
Recoveries on loans	110	219	426	595
Loans charged off	(161)	(168)	(483)	(854)
Ending balance	2,803	2,629	2,803	2,629
Residential
Allowance for loan losses:
Beginning balance	15,113	14,788	14,157	12,343
Provision for losses	333	(90)	3,236	3,565
Recoveries on loans	311	174	946	968
Loans charged off	(1,051)	(1,745)	(3,633)	(3,749)
Ending balance	14,706	13,127	14,706	13,127
Finance Leases
Allowance for loan losses:
Beginning balance	36			3
Provision for losses	17		68	(4)
Recoveries on loans	3		3	1
Loans charged off			(15)
Ending balance	$ 56		$ 56