Commitments and Contingencies - Commitments and Letters of Credit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Commitment And Contingencies [Line Items]
Total Commitments	$ 1,542,026	$ 1,501,346
Standby letters of credit
Commitment And Contingencies [Line Items]
Total Commitments	77,134	80,918
Commitments to extend credit
Commitment And Contingencies [Line Items]
Total Commitments	$ 1,464,892	$ 1,420,428