Accumulated change, net of tax, in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges. Includes an entity's share of an equity investee's Increase or Decrease in deferred hedging gains or losses.

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The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

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The estimated value of gains (losses), net anticipated to be transferred in the future from accumulated other comprehensive income into earnings.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

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Carrying amount of non-derivative debt instruments designated as net investment hedges.

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Forward commitments to sell mortgage loans.

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Hedged mortgage loans held for sale.

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Unfunded mortgage loan commitments.

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Derivative Instruments - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Dec. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Realized and unrealized gains (losses) on derivatives classified as cash flow hedges recorded in other comprehensive income (loss)			$ 51	$ 112
Non-derivative debt instruments designated as net investment hedges			1,100	$ 1,100
Fair value of derivatives under collateral agreements in a net liability position			353
Collateral posted by company netted against net liability position			271
Forward commitments to sell mortgage loans			4,000
Hedged mortgage loans held for sale			2,100
Unfunded mortgage loan commitments			$ 2,600
Scenario, Forecast [Member]
Derivative [Line Items]
Estimated gain to be reclassified from other comprehensive income (loss) into earnings	$ 10	$ 11