Consolidated Statements Of Stockholders' Equity - USD ($) shares in Thousands, $ in Millions	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjustment Retained Earnings	Cumulative Effect, Period of Adoption, Adjustment Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent	$ 4,595	$ 3	$ 657	$ 4,062	$ (127)
Beginning balance (in shares) at Mar. 31, 2018		306,370
Beginning balance at Mar. 31, 2018	4,595	$ 3	657	4,062	(127)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent	4,595	$ 3	657	4,062	(127)
Stockholders' Equity Attributable to Parent | Accounting Standards Update 2014-09 [Member]						$ 612	$ 590
Stockholders' Equity Attributable to Parent | Accounting Standards Update 2018-02 [Member]							(1)
Ending balance (Accounting Standards Update 2014-09 [Member]) at Apr. 01, 2018						612	590
Ending balance (Accounting Standards Update 2018-02 [Member]) at Apr. 01, 2018							(1)
Beginning balance (in shares) at Mar. 31, 2018		306,370
Beginning balance at Mar. 31, 2018	4,595	$ 3	657	4,062	(127)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Other comprehensive income (loss) before reclassifications	81
Other comprehensive income (loss) before reclassifications | Accounting Standards Update 2014-09 [Member]								$ 22
Amounts reclassified from accumulated other comprehensive income (loss)	(7)
Amounts reclassified from accumulated other comprehensive income (loss) | Accounting Standards Update 2018-02 [Member]								$ 1
Stockholders' Equity Attributable to Parent	5,331	$ 3	0	5,358	(30)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	1,093			1,019	74
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	284		284
Stock Issued During Period, Shares, New Issues		2,722
Stock Issued During Period, Value, New Issues	(61)		(61)
Stock Repurchased and Retired During Period, Shares		(10,985)
Stock Repurchased and Retired During Period, Value	(1,192)		(880)	(312)
Ending balance (in shares) at Mar. 31, 2019		298,107
Ending balance at Mar. 31, 2019	5,331	$ 3	0	5,358	(30)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent | Accounting Standards Update 2014-09 [Member]						$ 612	590
Stockholders' Equity Attributable to Parent | Accounting Standards Update 2018-02 [Member]							$ (1)
Stockholders' Equity Attributable to Parent	5,331	3	0	5,358	(30)
Other comprehensive income (loss) before reclassifications	44
Amounts reclassified from accumulated other comprehensive income (loss)	(64)
Stockholders' Equity Attributable to Parent	7,461	$ 3	0	7,508	(50)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	3,019			3,039	(20)
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	347		347
Stock Issued During Period, Shares, New Issues		2,623
Stock Issued During Period, Value, New Issues	(29)		(29)
Stock Repurchased and Retired During Period, Shares		(12,317)
Stock Repurchased and Retired During Period, Value	$ (1,207)		(318)	(889)
Ending balance (in shares) at Mar. 31, 2020	288,000	288,413
Ending balance at Mar. 31, 2020	$ 7,461	$ 3	0	7,508	(50)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent	7,461	3	0	7,508	(50)
Other comprehensive income (loss) before reclassifications	(25)
Amounts reclassified from accumulated other comprehensive income (loss)	25
Stockholders' Equity Attributable to Parent	7,461	$ 3	0	7,887	(50)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	837			837	0
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	435		435
Stock Issued During Period, Shares, New Issues		3,685
Stock Issued During Period, Value, New Issues	(66)		(66)
Stock Repurchased and Retired During Period, Shares		(5,633)
Stock Repurchased and Retired During Period, Value	$ (729)		(369)	(360)
Common Stock, Dividends, Per Share, Declared	$ 0.34
Dividends, Common Stock, Cash	$ 98			98
Ending balance (in shares) at Mar. 31, 2021	286,000	286,465
Ending balance at Mar. 31, 2021	$ 7,840	$ 3	0	7,887	(50)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stockholders' Equity Attributable to Parent	$ 7,840	$ 3	$ 0	$ 7,887	$ (50)