Allowance for Credit Losses - Provision 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
Receivables [Abstract]
Provision for loan losses	$ 6,592	$ 3,710	$ 17,294	$ 6,112
Provision for unfunded letters of credit	550	(78)	796	(10)
Total provision for credit losses	$ 7,142	$ 3,632	$ 18,090	$ 6,102