Consolidated Balance Sheet (parenthetical) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Financing Receivable, Allowance for Credit Loss	$ (1,223)	$ (1,305)	$ (1,231)	$ (513)

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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