Long-Term Debt (Details) (USD $)	1 Months Ended
	Jul. 31, 2012	Jul. 26, 2012 Y	Jun. 30, 2012 Y	May 16, 2012 Y
4 5/8% Senior Notes due 2017
Debt Instrument
Aggregate principal amount				$ 900,000,000
Interest rate (as a percent)			4.625%	4.625%
Term of debt instrument (in years)			5	5
Debt instrument issuance as a percentage of the face amount				100.00%
Percentage of principal amount at which the entity may redeem some or all of the notes at any time (as a percent)			100.00%
Percentage of principal amount at which notes may be required to be repurchased in event of change of control (as a percent)			101.00%
4 5/8% Senior Notes due 2017 | Redemption Prior to July 15, 2015
Debt Instrument
Maximum percentage of the aggregate principal amount of notes with net proceeds of certain equity offerings or capital contributions			35.00%
5 7/8% Senior Notes due 2022
Debt Instrument
Aggregate principal amount				1,000,000,000
Additional borrowings	$ 1,000,000,000
Interest rate (as a percent)		5.875%	5.875%	5.875%
Term of debt instrument (in years)		10	10	10
Debt instrument issuance as a percentage of the face amount		100.75%		100.00%
Percentage of principal amount at which the entity may redeem some or all of the notes at any time (as a percent)			100.00%
Percentage of principal amount at which notes may be required to be repurchased in event of change of control (as a percent)			101.00%
5 7/8% Senior Notes due 2022 | Redemption Prior to July 15, 2015
Debt Instrument
Maximum percentage of the aggregate principal amount of notes with net proceeds of certain equity offerings or capital contributions			35.00%