Long-Term Debt (Details Textuals) (USD $)	1 Months Ended	12 Months Ended								1 Months Ended					1 Months Ended					1 Months Ended			12 Months Ended		1 Months Ended			12 Months Ended			1 Months Ended	12 Months Ended		12 Months Ended
	Feb. 28, 2013	Dec. 31, 2013 Rate	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Bank Credit Agreement [Member] Rate	Nov. 01, 2013 Bank Credit Agreement [Member]	Mar. 31, 2010 Bank Credit Agreement [Member]	Dec. 31, 2011 7 1/2% Senior Subordinated Notes due 2013 [Member]	Dec. 31, 2011 7 1/2% Senior Subordinated Notes due 2015 [Member]	May 31, 2013 9 1/2% Senior Subordinated Notes due 2016 [Member] Rate	Feb. 28, 2013 9 1/2% Senior Subordinated Notes due 2016 [Member] Rate	Dec. 31, 2013 9 1/2% Senior Subordinated Notes due 2016 [Member]	Jan. 31, 2013 9 1/2% Senior Subordinated Notes due 2016 [Member]	Dec. 31, 2012 9 1/2% Senior Subordinated Notes due 2016 [Member]	Mar. 31, 2013 9 3/4% Senior Subordinated Notes due 2016 [Member] Rate	Feb. 28, 2013 9 3/4% Senior Subordinated Notes due 2016 [Member] Rate	Dec. 31, 2013 9 3/4% Senior Subordinated Notes due 2016 [Member]	Jan. 31, 2013 9 3/4% Senior Subordinated Notes due 2016 [Member]	Dec. 31, 2012 9 3/4% Senior Subordinated Notes due 2016 [Member]	Feb. 28, 2010 8 1/4% Senior Subordinated Notes due 2020 [Member]	Dec. 31, 2013 8 1/4% Senior Subordinated Notes due 2020 [Member]	Dec. 31, 2012 8 1/4% Senior Subordinated Notes due 2020 [Member]	Dec. 31, 2013 8 1/4% Senior Subordinated Notes due 2020 [Member] Debt Instrument, Redemption, Period One [Member] Rate	Dec. 31, 2013 8 1/4% Senior Subordinated Notes due 2020 [Member] Initial Redemption Period with Make-Whole Premium [Member]	Feb. 28, 2011 6 3/8% Senior Subordinated Notes due 2021 [Member]	Dec. 31, 2013 6 3/8% Senior Subordinated Notes due 2021 [Member]	Dec. 31, 2012 6 3/8% Senior Subordinated Notes due 2021 [Member]	Dec. 31, 2013 6 3/8% Senior Subordinated Notes due 2021 [Member] Debt Instrument, Redemption, Period One [Member] Rate	Dec. 31, 2013 6 3/8% Senior Subordinated Notes due 2021 [Member] Initial Redemption Period with Proceeds from Equity Offering [Member] Rate	Dec. 31, 2013 6 3/8% Senior Subordinated Notes due 2021 [Member] Initial Redemption Period with Make-Whole Premium [Member]	Feb. 28, 2013 4 5/8% Senior Subordinated Notes due 2023 [Member]	Dec. 31, 2013 4 5/8% Senior Subordinated Notes due 2023 [Member]	Dec. 31, 2012 4 5/8% Senior Subordinated Notes due 2023 [Member]	Dec. 31, 2013 4 5/8% Senior Subordinated Notes due 2023 [Member] Debt Instrument, Redemption, Period One [Member] Rate	Dec. 31, 2013 4 5/8% Senior Subordinated Notes due 2023 [Member] Initial Redemption Period with Proceeds from Equity Offering [Member] Rate	Dec. 31, 2013 4 5/8% Senior Subordinated Notes due 2023 [Member] Initial Redemption Period with Make-Whole Premium [Member]	Dec. 31, 2013 Minimum [Member] Bank Credit Agreement [Member]	Dec. 31, 2013 Maximum [Member] Bank Credit Agreement [Member]	Dec. 31, 2013 Eurodollar Rate [Member] Minimum [Member] Bank Credit Agreement [Member] Rate	Dec. 31, 2013 Eurodollar Rate [Member] Maximum [Member] Bank Credit Agreement [Member] Rate	Dec. 31, 2013 Base Rate [Member] Minimum [Member] Bank Credit Agreement [Member] Rate	Dec. 31, 2013 Base Rate [Member] Maximum [Member] Bank Credit Agreement [Member] Rate	Dec. 31, 2013 Base Rate Option 2 [Member] Bank Credit Agreement [Member] Rate	Dec. 31, 2013 Base Rate Option 3 [Member] Bank Credit Agreement [Member] Rate
$1.6 Billion Revolving Credit Agreement [Abstract]
Borrowing base of Bank Credit Agreement						$ 1,600,000,000.0	$ 1,600,000,000.0
Line of Credit Facility, Interest Rate During Period					1.90%
Current Ratio Requirement					1.0
Total Debt to EBITDA Requirement					4.25																											2.5
Interest rate margins on Bank Credit Agreement																																							1.50%	2.50%	0.50%	1.50%	0.50%	1.00%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage																																					0.375%	0.50%
Minimum Bank Credit Facility Availability Percentage To Pay Dividends		10.00%
Debt Instruments [Abstract]
Subordinated Debt												0	224,900,000	234,038,000			0	426,400,000	412,781,000		996,273,000	996,273,000				400,000,000	400,000,000					1,200,000,000	0
Debt Instrument, Redemption Price, Percentage										104.75%	106.869%				104.875%	105.425%							104.125%	100.00%				103.188%	106.375%	100.00%				102.313%	104.625%	100.00%
Debt Instrument, Percentage of Principal Amount Available To Be Redeemed																													35.00%						35.00%
Debt Instrument, Repurchased Face Amount								225,000,000	300,000,000	38,200,000	186,700,000				234,700,000	191,700,000				3,700,000
Loss on early extinguishment of debt		44,651,000	0	16,131,000
Face value of senior subordinated notes																				1,000,000,000					400,000,000						1,200,000,000
Proceeds from issuance of subordinated long-term debt, net of commissions and fees																				980,000,000					393,000,000						1,180,000,000
Interest rate on senior subordinated notes												9.50%					9.75%				8.25%					6.375%						4.625%
Selling Price Of Debt Instrument	100.00%																			100.00%					100.00%
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed																								100.00%						100.00%						100.00%
Interest in guarantor subsidiaries		100.00%
Lease period included in long term transportation service agreement		20 years
Unamortized debt issuance costs		$ 58,900,000	$ 56,500,000