Borrowings - Schedule of Short-term Borrowings (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Short-term Debt [Line Items]
Amount	$ 617,363	$ 2,669,145
Weighted-average Rate	0.25%	1.75%
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:LongTermDebtAndCapitalLeaseObligations	us-gaap:LongTermDebtAndCapitalLeaseObligations
FHLB advances
Short-term Debt [Line Items]
Amount	$ 400,000	$ 2,450,000
Weighted-average Rate	0.33%	1.85%
Collateralized deposits
Short-term Debt [Line Items]
Amount	$ 217,363	$ 219,145
Weighted-average Rate	0.11%	0.64%