Subsequent Events (Details) (USD $)	3 Months Ended		9 Months Ended		3 Months Ended	6 Months Ended	1 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Subsequent Events [Member]	Jun. 30, 2012 Subsequent Events [Member]	Aug. 31, 2011 Subsequent Events [Member] Senior Notes due 2023 [Member]	Sep. 30, 2012 Subsequent Events [Member] Senior Notes due 2023 [Member]	Aug. 15, 2012 Subsequent Events [Member] Senior Notes due 2023 [Member]	Oct. 31, 2012 Subsequent Events [Member] Notes due April 2015 [Member]	Sep. 30, 2012 Subsequent Events [Member] Notes due April 2015 [Member]	Oct. 31, 2012 Subsequent Events [Member] Senior Notes due 2017 [Member]	Sep. 30, 2012 Subsequent Events [Member] Senior Notes due 2017 [Member]
Subsequent Event [Line Items]
Aggregate principal amount of debt under registered offering								$ 250,000,000	$ 600,000,000
Issue price expressed as a percentage of principal amount (in hundredths)								104.25%
Effective yield on debt (in hundredths)								6.551%
Net proceeds from offering							255,900,000
Interest Rate (in hundredths)								7.125%					8.25%
Aggregate principal amount to be purchased											75,700,000		59,300,000
Amount of consideration for purchase of note					154,700,000
Losses on early extinguishment of debt	(245,000)	0	(71,063,000)	0		19,300,000
Senior Notes										$ 374,800,000		$ 1,040,700,000