Loans and Allowance for Credit Losses - Summary of Average Recorded Investment in Impaired Originated and ANCI Loans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accounts Notes And Loans Receivable [Line Items]
Average recorded investment	$ 85,336	$ 66,584
Commercial and Industrial
Accounts Notes And Loans Receivable [Line Items]
Average recorded investment	83,085	63,941
Commercial and Industrial | General C&I
Accounts Notes And Loans Receivable [Line Items]
Average recorded investment	38,358	4,979
Commercial and Industrial | Energy Sector
Accounts Notes And Loans Receivable [Line Items]
Average recorded investment	17,297	47,969
Commercial and Industrial | Restaurant Industry
Accounts Notes And Loans Receivable [Line Items]
Average recorded investment	22,957	10,993
Commercial and Industrial | Healthcare
Accounts Notes And Loans Receivable [Line Items]
Average recorded investment	4,473
Consumer
Accounts Notes And Loans Receivable [Line Items]
Average recorded investment	1,789	1,981
Consumer | Residential Real Estate
Accounts Notes And Loans Receivable [Line Items]
Average recorded investment	1,534	1,583
Consumer | Other
Accounts Notes And Loans Receivable [Line Items]
Average recorded investment	255	398
Small Business Lending
Accounts Notes And Loans Receivable [Line Items]
Average recorded investment	$ 462	$ 662