Mortgage Banking - Additional information (Details) - USD ($)	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Mortgage Banking [Abstract]
Residential Mortgage Loans, Unpaid Balance	$ 3,000,000,000.0		$ 3,000,000,000.0		$ 1,460,000,000
Accrued Liabilities and Other Liabilities	43,000		43,000		$ 43,000
Expenses (credit) relating to secondary market buy-back activity	$ 0	$ 0	$ 0	$ 0

Amount of expenses incurred but not yet paid nor invoiced, and liabilities classified as other.

No definition available.

Name:	us-gaap_AccruedLiabilitiesAndOtherLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant