Borrowings - Additional Information (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Debt Disclosure
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Maximum Amount Available	$ 2,900,000,000	$ 3,000,000,000.0
Federal Home Loan Bank Advances And Letters Of Credit Amount Used	500,000,000	500,000,000
Assets sold under agreements to repurchase	86,834,000	121,303,000
Other short-term borrowings	0	0
Advances with FRB
Debt Disclosure
Line Of Credit Facility Current Borrowing Capacity	1,300,000,000	1,400,000,000
Federal Home Loan Bank
Debt Disclosure
Line Of Credit Facility Capacity Available For Specific Purpose Other Than For Trade Purchases	$ 900,000,000	$ 900,000,000