Commitments and Contingencies - Schedule of Total Unfunded Commitments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Commitment And Contingencies [Line Items]
Total unfunded commitments	$ 749,549	$ 784,077
Commitments to fund loans [Member]
Commitment And Contingencies [Line Items]
Total unfunded commitments	204,282	183,946
Unfunded Commitment Line Of Credit [Member]
Commitment And Contingencies [Line Items]
Total unfunded commitments	534,112	589,573
Commercial And Standby Letters Of Credit [Member]
Commitment And Contingencies [Line Items]
Total unfunded commitments	$ 11,155	$ 10,558