Fair Value Measurements - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 EUR (€)	Dec. 31, 2019 USD ($)	Dec. 31, 2019 EUR (€)
Derivatives, Fair Value [Line Items]
Carrying amount of our investments without readily determinable fair values	$ 317,000,000		$ 317,000,000			$ 284,000,000
Derivative asset fair value of collateral	300,000,000		300,000,000
Interest rate swaps
Derivatives, Fair Value [Line Items]
Net investment hedge	18,156,000,000		18,156,000,000			17,004,000,000
Interest rate swaps | Fair Value Hedges
Derivatives, Fair Value [Line Items]
Notional amount of derivative instruments entered during period	1,100,000,000	$ 0	3,500,000,000	$ 510,000,000
Notional amount of derivative settled during period	0	2,100,000,000	2,400,000,000	3,300,000,000
Ineffectiveness portion of interest rate swaps				88,000,000
Cross currency swaps
Derivatives, Fair Value [Line Items]
Net investment hedge	24,740,000,000		24,740,000,000			23,070,000,000
Cross currency swaps | Cash Flow Hedging
Derivatives, Fair Value [Line Items]
Notional amount of derivative instruments entered during period	0	2,100,000,000	3,300,000,000	5,600,000,000
Notional amount of derivative settled during period	0	0	1,600,000,000	0
Pre-tax gains (loss) recognized in other comprehensive income (loss)	1,500,000,000	(658,000,000)	(420,000,000)	(986,000,000)
Forward starting interest rate swaps
Derivatives, Fair Value [Line Items]
Net investment hedge	2,000,000,000		2,000,000,000			3,000,000,000
Forward starting interest rate swaps | Cash Flow Hedging
Derivatives, Fair Value [Line Items]
Notional amount of derivative instruments entered during period	0	0	0	0
Notional amount of derivative settled during period	0	0	1,000,000,000.0	1,000,000,000.0
Pre-tax gains (loss) recognized in other comprehensive income (loss)	141,000,000	(350,000,000)	(668,000,000)	(847,000,000)
Treasury rate locks | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount of derivative instruments entered during period	0	0	1,600,000,000	0
Notional amount of derivative settled during period	0	0	1,600,000,000	0
Pre-tax gains (loss) recognized in other comprehensive income (loss)	0	0		0
Treasury rate locks | Cash Flow Hedging
Derivatives, Fair Value [Line Items]
Notional amount of derivative instruments entered during period	0	0	500,000,000	0
Notional amount of derivative settled during period	0	0	500,000,000	0
Pre-tax gains (loss) recognized in other comprehensive income (loss)	0	0		0
Euro Denominated Debt | Net Investment Hedges
Derivatives, Fair Value [Line Items]
Net investment hedge | €					€ 750,000,000		€ 750,000,000
Foreign exchange forwards
Derivatives, Fair Value [Line Items]
Net investment hedge	1,300,000,000		1,300,000,000			$ 1,130,000,000
Foreign exchange forwards | Not Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Notional amount of derivative instruments entered during period	3,400,000,000	3,100,000,000	10,300,000,000	9,200,000,000
Notional amount of derivative settled during period	$ 3,100,000,000	$ 3,000,000,000.0	10,200,000,000	8,600,000,000
Pre-tax gains (loss) recognized in other comprehensive income (loss)			$ 89,000,000	$ (53,000,000)