Loans and Allowance for Credit Losses - Summary of Loans Held For Sale (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Accounts Notes And Loans Receivable [Line Items]
Loans held for sale	$ 209,346	$ 59,461
Residential Mortgage
Accounts Notes And Loans Receivable [Line Items]
Loans held for sale	19,764	17,004
Commercial Loans
Accounts Notes And Loans Receivable [Line Items]
Loans held for sale	$ 189,582	$ 42,457