Loans and Allowance for Credit Losses Activity in the Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	$ 165,108	$ 169,453	$ 171,412	$ 185,931
Loans charged off	(7,672)	(5,561)	(29,573)	(26,697)
Recoveries of loans previously charged off	3,592	4,503	15,148	10,661
Net loans charged off	(4,080)	(1,058)	(14,425)	(16,036)
Provision for credit losses	4,141	1,000	8,182	(500)
Balance at end of period	$ 165,169	$ 169,395	$ 165,169	$ 169,395