Loans and Allowance for Credit Losses Non-Performing Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Receivables [Abstract]
Non-accrual loans	$ 111,116	$ 124,749
Loans 90 days or more past due and still accruing	12,628	10,010
Total non-performing loans	123,744	134,759
Other real estate owned (OREO)	11,181	9,823
Total non-performing assets	$ 134,925	$ 144,582