Changes in Accumulated Other Comprehensive Income by Component (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jun. 30, 2013		Jun. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balances as of March 31, 2013	$ 69	[1]
Other comprehensive income (loss) before reclassifications	(15)
Amounts reclassified from accumulated other comprehensive income	2
Net current-period other comprehensive income (loss)	(13)		(58)
Balances as of June 30, 2013	56
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balances as of March 31, 2013	(4)
Other comprehensive income (loss) before reclassifications	(1)
Amounts reclassified from accumulated other comprehensive income	0
Net current-period other comprehensive income (loss)	(1)
Balances as of June 30, 2013	(5)
Unrealized Gains (Losses) on Derivative Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balances as of March 31, 2013	0
Other comprehensive income (loss) before reclassifications	(2)
Amounts reclassified from accumulated other comprehensive income	2
Net current-period other comprehensive income (loss)	0
Balances as of June 30, 2013	0
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balances as of March 31, 2013	73
Other comprehensive income (loss) before reclassifications	(12)
Amounts reclassified from accumulated other comprehensive income	0
Net current-period other comprehensive income (loss)	(12)
Balances as of June 30, 2013	$ 61

[1] Derived from audited consolidated financial statements.