Allowance for Loan Losses - Change in Allowance for Loan Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Changes in the allowance for loan losses
Balance at the beginning of period	$ 35,569	$ 35,606	$ 34,852
Provision charged to operations	18,040	15,512	16,330
Loans charged off	(21,170)	(20,317)	(19,846)
Recoveries of loans previously charged off	4,627	4,768	4,270
Balance at the end of period	$ 37,066	$ 35,569	$ 35,606