Loans and Allowance for Credit Losses Allowance for Credit Losses (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015
Receivables [Abstract]
Allowance for loan losses	$ 172,342	$ 170,076	$ 168,679	$ 162,546	$ 163,841	$ 169,054
Reserve for unfunded lending commitments	2,656		2,646
Allowance for credit losses	$ 174,998	$ 172,647	$ 171,325	$ 165,108	$ 166,065	$ 171,412