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, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of period	$ 176,019	$ 172,647	$ 176,084	$ 171,325
Loans charged off	(42,160)	(8,715)	(48,557)	(18,122)
Recoveries of loans previously charged off	2,271	4,366	4,633	10,295
Net loans charged off	(39,889)	(4,349)	(43,924)	(7,827)
Provision for credit losses	33,117	6,700	37,087	11,500
Balance at end of period	$ 169,247	$ 174,998	$ 169,247	$ 174,998