Loans and Allowance for Credit Losses Activity in the Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	$ 179,658	$ 199,006	$ 185,931	$ 204,917
Loans charged off	(15,372)	(11,476)	(21,136)	(21,744)
Recoveries of loans previously charged off	2,967	2,412	6,158	4,269
Net loans charged off	(12,405)	(9,064)	(14,978)	(17,475)
Provision for credit losses	2,200	3,500	(1,500)	6,000
Balance at end of period	$ 169,453	$ 193,442	$ 169,453	$ 193,442