Fair Value Measurements - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 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	$ 301,000,000		$ 301,000,000			$ 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	16,996,000,000		16,996,000,000			17,004,000,000
Interest rate swaps | Fair Value Hedges
Derivatives, Fair Value [Line Items]
Notional amount of derivative instruments entered during period	0	$ 0	2,400,000,000	$ 510,000,000
Notional amount of derivative settled during period	929,000,000	0	2,400,000,000	1,200,000,000
Ineffectiveness portion of interest rate swaps			56,000,000	60,000,000
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	3,300,000,000	3,500,000,000	3,300,000,000	3,500,000,000
Notional amount of derivative settled during period	1,600,000,000	0	1,600,000,000	0
Pre-tax gains (loss) recognized in other comprehensive income (loss)	1,000,000,000.0	(340,000,000)	(1,900,000,000)	(328,000,000)
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)		(293,000,000)	(809,000,000)	(497,000,000)
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	960,000,000		960,000,000			$ 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	4,300,000,000	3,100,000,000	6,900,000,000	6,100,000,000
Notional amount of derivative settled during period	4,200,000,000	$ 3,000,000,000.0	$ 7,100,000,000	$ 5,600,000,000
Pre-tax gains (loss) recognized in other comprehensive income (loss)	$ 81,000,000