Derivatives, Hedging Activities and Interest Expense - Additional Information (Details) - USD ($) $ in Millions	Mar. 31, 2021	Mar. 31, 2020
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Collateral held in excess of the fair value of derivative assets	$ 2	$ 29
Initial margin and collateral posted in excess of the fair value of derivative liabilities	$ 132	$ 10

Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
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-Publisher FASB
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Name:	us-gaap_DerivativeCollateralObligationToReturnCash
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant