Other Borrowings - Summary of Short-term Credit Lines Available for Use (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Federal Home Loan Bank Line
Debt Instrument [Line Items]
Short-term credit lines available for use	$ 1,883,967	$ 2,016,212
Federal Reserve Bank of Chicago Discount Window Line
Debt Instrument [Line Items]
Short-term credit lines available for use	885,510	874,677
Available Federal Funds Line
Debt Instrument [Line Items]
Short-term credit lines available for use	$ 115,000	$ 115,000