Loans and Allowance for Credit Losses Activity in the Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	$ 171,412	$ 185,931
Loans charged off	(11,155)	(5,764)
Recoveries of loans previously charged off	4,278	3,191
Net loans charged off	(6,877)	(2,573)
Provision for credit losses	1,530	(3,700)
Balance at end of period	$ 166,065	$ 179,658