Changes in Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2020		Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ (50)	[1]	$ (30)
Other comprehensive income (loss) before reclassifications	3		23
Amounts reclassified from accumulated other comprehensive income (loss)	(5)		(10)
Total other comprehensive income (loss), net of tax	(2)		13
Ending balance	(52)		(17)
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(4)		(1)
Other comprehensive income (loss) before reclassifications	11		3
Amounts reclassified from accumulated other comprehensive income (loss)	0		0
Total other comprehensive income (loss), net of tax	11		3
Ending balance	7		2
Unrealized Gains (Losses) on Derivative Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	39		22
Other comprehensive income (loss) before reclassifications	(32)		19
Amounts reclassified from accumulated other comprehensive income (loss)	(5)		(10)
Total other comprehensive income (loss), net of tax	(37)		9
Ending balance	2		31
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(85)		(51)
Other comprehensive income (loss) before reclassifications	24		1
Amounts reclassified from accumulated other comprehensive income (loss)	0		0
Total other comprehensive income (loss), net of tax	24		1
Ending balance	$ (61)		$ (50)

[1] Derived from audited Consolidated Financial Statements.