Debt - Extinguishment of Debt (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Jun. 30, 2013
Unsecured Senior Notes Due 2013 [Member]
Extinguishment of Debt [Line Items]
Extinguishment of Debt, Amount	$ 250
Extinguishment of Debt, Interest Rate	5.125%
Debt Instrument Early Redemption Date	Aug. 28, 2012
Bridge Loan [Member]
Extinguishment of Debt [Line Items]
Extinguishment of Debt, Amount	$ 260
Debt Instrument Early Redemption Date	Jan. 11, 2103