Loans and Allowance for Credit Losses - Summary of Originated and ANCI Loans that Were Modified Into TDRs (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) TDR	Dec. 31, 2017 USD ($) TDR	Dec. 31, 2016 USD ($) TDR
Financing Receivable Modifications [Line Items]
Number of TDRs | TDR	6	6	9
Recorded Investment | $	$ 30,385	$ 16,904	$ 44,695
Commercial and Industrial
Financing Receivable Modifications [Line Items]
Number of TDRs | TDR	4	3	6
Recorded Investment | $	$ 30,244	$ 16,027	$ 43,609
Consumer
Financing Receivable Modifications [Line Items]
Number of TDRs | TDR		2	2
Recorded Investment | $		$ 739	$ 534
Small Business Lending
Financing Receivable Modifications [Line Items]
Number of TDRs | TDR	2	1	1
Recorded Investment | $	$ 141	$ 138	$ 552