Other Borrowings - Summary of Short-term Credit Lines Available for Use (Details) - USD ($) $ in Thousands		Sep. 30, 2020	Dec. 31, 2019
Available Federal Funds Line
Debt Instrument [Line Items]
Short-term credit lines available for use	[1]	$ 115,000	$ 115,000
Federal Reserve Bank of Chicago Discount Window Line
Debt Instrument [Line Items]
Short-term credit lines available for use		968,693	547,798
Federal Home Loan Bank Line
Debt Instrument [Line Items]
Short-term credit lines available for use		$ 1,999,298	$ 1,390,698

[1] The Company did not have an outstanding balance on its federal funds lines as of September 30, 2020 and December 31, 2019.