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Stockholders' Equity - Narrative (Details) $ / shares in Units, shares in Millions	1 Months Ended						2 Months Ended	3 Months Ended	4 Months Ended	8 Months Ended	10 Months Ended	12 Months Ended
	Jul. 31, 2018 $ / shares	Mar. 31, 2018 USD ($) shares	Aug. 31, 2017 USD ($)	Jun. 30, 2017 USD ($)	Apr. 30, 2017 shares	Mar. 31, 2017 USD ($) shares	Apr. 30, 2017 $ / shares shares	Jun. 30, 2018 $ / shares shares	Mar. 31, 2019 USD ($) vote $ / shares shares	Mar. 31, 2018 USD ($) shares	Mar. 31, 2018 USD ($) shares	Mar. 31, 2019 USD ($) vote $ / shares shares	Mar. 31, 2018 USD ($) $ / shares shares	Mar. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2018 USD ($)	May 31, 2018 USD ($)	Oct. 31, 2016 USD ($)	Mar. 31, 2016 USD ($)
Dividends Payable [Line Items]
Number of votes | vote									1			1
Cash dividends declared per common share (in dollars per share) | $ / shares												$ 1.51	$ 1.30	$ 1.12
Additional authorized																$ 4,000,000,000	$ 4,000,000,000.0
Shares bought (in shares) | shares												13.5	10.5	15.5
Shares repurchased												$ 1,627,000,000	$ 1,650,000,000	$ 2,250,000,000
Average price paid per share (in dollars per share) | $ / shares								$ 143.66				$ 130.72	$ 151.06	$ 141.16
Total authorization outstanding for repurchases of common stock		$ 1,096,000,000				$ 2,746,000,000			$ 3,469,000,000	$ 1,096,000,000	$ 1,096,000,000	$ 3,469,000,000	$ 1,096,000,000	$ 2,746,000,000				$ 996,000,000
Repurchase of common stock												$ 1,627,000,000	1,650,000,000	2,250,000,000
Treasury stock retired (in shares) | shares												5.0
Retirement of common stock												$ 542,000,000
Other comprehensive income (loss) before reclassifications												(207,000,000)	604,000,000
Net foreign currency translation gains (losses)												(198,000,000)	609,000,000	(659,000,000)
Gains (losses) from net investment hedges												$ 259,000,000	$ (268,000,000)	$ (13,000,000)
Minimum
Dividends Payable [Line Items]
Cash dividends declared per common share (in dollars per share) | $ / shares	$ 0.34
Maximum
Dividends Payable [Line Items]
Cash dividends declared per common share (in dollars per share) | $ / shares	$ 0.39
Treasury Stock
Dividends Payable [Line Items]
Repurchase of common stock (in shares) | shares												13.0	11.0	16.0
Repurchase of common stock												$ 1,777,000,000	$ 1,614,000,000	$ 2,200,000,000
Retained Earnings
Dividends Payable [Line Items]
Retirement of common stock												472,000,000
Additional Paid-in Capital
Dividends Payable [Line Items]
Repurchase of common stock												(150,000,000)	36,000,000	50,000,000
Retirement of common stock												70,000,000
Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest
Dividends Payable [Line Items]
Other comprehensive income (loss) before reclassifications												(431,000,000)	804,000,000	(644,000,000)
Net foreign currency translation gains (losses)												(431,000,000)	804,000,000	$ (624,000,000)
Accumulated Foreign Currency Adjustment Attributable to Noncontrolling Interest
Dividends Payable [Line Items]
Net foreign currency translation gains (losses)												(61,000,000)	189,000,000
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Including Portion Attributable to Noncontrolling Interest
Dividends Payable [Line Items]
Other comprehensive income (loss) before reclassifications												$ (5,000,000)	$ (4,000,000)
Open Market Transactions
Dividends Payable [Line Items]
Average price paid per share (in dollars per share) | $ / shares													$ 144.43	$ 140.96
Repurchase of common stock (in shares) | shares													3.5	14.1
Repurchase of common stock													$ 500,000,000	$ 2,000,000,000
Accelerated Share Repurchase
Dividends Payable [Line Items]
Additional authorized															$ 250,000,000
Shares bought (in shares) | shares					0.3	1.4	1.7		2.1
Shares repurchased		$ 500,000,000	$ 400,000,000	$ 250,000,000		$ 250,000,000
Average price paid per share (in dollars per share) | $ / shares							$ 143.19		$ 117.98
June 2017 Accelerated Share Repurchase
Dividends Payable [Line Items]
Shares bought (in shares) | shares											1.5
August 2017 Accelerated Share Repurchase
Dividends Payable [Line Items]
Shares bought (in shares) | shares										2.7
March 2018 ASR Program
Dividends Payable [Line Items]
Shares bought (in shares) | shares		2.5						1.0
May 2018 Share Repurchase Program
Dividends Payable [Line Items]
Additional authorized																4,000,000,000.0
Shares bought (in shares) | shares												10.4
Shares repurchased												$ 1,400,000,000
Average price paid per share (in dollars per share) | $ / shares												$ 132.14
Total authorization outstanding for repurchases of common stock																$ 5,100,000,000

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