Acquisitions (Details) (USD $)	0 Months Ended		0 Months Ended
	Oct. 02, 2011 Meraux Acquisition [Member]	Dec. 31, 2011 Meraux Acquisition [Member]	Aug. 01, 2011 Pembroke Acquisition [Member]	Dec. 31, 2011 Pembroke Acquisition [Member]
Acquisitions (Textual)
Effective date of acquisition	October 1, 2011		August 1, 2011
Purchase price of acquired entity	$ 586,000,000	$ 547,000,000	$ 1,800,000,000	$ 1,700,000,000
Purchase price of working capital			$ 1,100,000,000
Percentage of outstanding shares acquired			100.00%