Loans and Allowance for Credit Losses - Summary of Individually Impaired ACI Loans and Pooled ACI Loans (Details) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Financing Receivable Impaired [Line Items]
Recorded Investment in Impaired Loans		$ 278,509	$ 249,133
Commercial and Industrial
Financing Receivable Impaired [Line Items]
Recorded Investment in Impaired Loans		261,381	242,048
Commercial Real Estate
Financing Receivable Impaired [Line Items]
Recorded Investment in Impaired Loans		8,139	985
Consumer
Financing Receivable Impaired [Line Items]
Recorded Investment in Impaired Loans		4,187	3,315
ACI Loans and Pooled ACI Loans
Financing Receivable Impaired [Line Items]
Recorded Investment in Impaired Loans	[1]	90,400	94,418
Unpaid Principal Balance		106,882	117,832
Related Specific Allowance		7,534	7,924
ACI Loans and Pooled ACI Loans | Commercial and Industrial
Financing Receivable Impaired [Line Items]
Recorded Investment in Impaired Loans	[1]	12,091	2,100
Unpaid Principal Balance		13,190	2,331
Related Specific Allowance		89	58
ACI Loans and Pooled ACI Loans | Commercial Real Estate
Financing Receivable Impaired [Line Items]
Recorded Investment in Impaired Loans	[1]	65,924	74,017
Unpaid Principal Balance		83,125	97,613
Related Specific Allowance		1,417	1,641
ACI Loans and Pooled ACI Loans | Consumer
Financing Receivable Impaired [Line Items]
Recorded Investment in Impaired Loans	[1]	12,385	18,301
Unpaid Principal Balance		10,567	17,888
Related Specific Allowance		$ 6,028	$ 6,225

[1] The recorded investment of a loan also includes any interest receivable, net unearned discount or fees, and unamortized premium or discount.