Borrowings and Other Short-term Liabilities (Additional Information) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Aug. 31, 2016
Debt Disclosure [Abstract]
FHLB advances	$ 7,810,000
Additional borrowing availability through the FHLB	230,100
Debt Instrument [Line Items]
Long-term borrowings, Amount	426,002	$ 372,882
Line of Credit
Debt Instrument [Line Items]
Long-term borrowings, Amount	$ 0	$ 19,963	$ 125,000