Other Borrowings - Summary of Short-term Credit Lines Available for Use (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Federal Reserve Bank of Chicago Discount Window Line
Debt Instrument [Line Items]
Short-term credit lines available for use	$ 310,345	$ 144,248
Available Federal Funds Line
Debt Instrument [Line Items]
Short-term credit lines available for use	$ 55,000	$ 55,000