Fair Value Measurements (Textuals) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended						9 Months Ended				9 Months Ended				3 Months Ended																																	9 Months Ended				9 Months Ended				9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2014 Oil contracts [Member]	Sep. 30, 2014 Oil contracts [Member] Options Held [Member]	Sep. 30, 2014 Oil contracts [Member] Maximum [Member] Options Held [Member]	Sep. 30, 2014 Oil contracts [Member] Minimum [Member] Options Held [Member]	Sep. 30, 2014 Natural gas contracts [Member]	Sep. 30, 2014 Natural gas contracts [Member] Options Held [Member]	Sep. 30, 2014 Natural gas contracts [Member] Maximum [Member] Options Held [Member]	Sep. 30, 2014 Natural gas contracts [Member] Minimum [Member] Options Held [Member]	Sep. 30, 2014 Equity Securities [Member]	Dec. 31, 2013 Equity Securities [Member]	Mar. 31, 2014 Auction Rate Securities [Member]	Dec. 31, 2013 Auction Rate Securities [Member]	Sep. 30, 2014 Swap [Member]	Dec. 31, 2013 Swap [Member]	Sep. 30, 2014 Commodity Option [Member]	Dec. 31, 2013 Commodity Option [Member]	Sep. 30, 2014 Quoted Prices In Active Markets for Identical Assets or Liabilities, Fair Value Inputs (Level 1) [Member]	Dec. 31, 2013 Quoted Prices In Active Markets for Identical Assets or Liabilities, Fair Value Inputs (Level 1) [Member]	Sep. 30, 2014 Quoted Prices In Active Markets for Identical Assets or Liabilities, Fair Value Inputs (Level 1) [Member] Equity Securities [Member]	Dec. 31, 2013 Quoted Prices In Active Markets for Identical Assets or Liabilities, Fair Value Inputs (Level 1) [Member] Equity Securities [Member]	Dec. 31, 2013 Quoted Prices In Active Markets for Identical Assets or Liabilities, Fair Value Inputs (Level 1) [Member] Auction Rate Securities [Member]	Sep. 30, 2014 Quoted Prices In Active Markets for Identical Assets or Liabilities, Fair Value Inputs (Level 1) [Member] Swap [Member]	Dec. 31, 2013 Quoted Prices In Active Markets for Identical Assets or Liabilities, Fair Value Inputs (Level 1) [Member] Swap [Member]	Sep. 30, 2014 Quoted Prices In Active Markets for Identical Assets or Liabilities, Fair Value Inputs (Level 1) [Member] Commodity Option [Member]	Dec. 31, 2013 Quoted Prices In Active Markets for Identical Assets or Liabilities, Fair Value Inputs (Level 1) [Member] Commodity Option [Member]	Sep. 30, 2014 Significant Other Observable Fair Value Inputs (Level 2) [Member]	Dec. 31, 2013 Significant Other Observable Fair Value Inputs (Level 2) [Member]	Sep. 30, 2014 Significant Other Observable Fair Value Inputs (Level 2) [Member] Equity Securities [Member]	Dec. 31, 2013 Significant Other Observable Fair Value Inputs (Level 2) [Member] Equity Securities [Member]	Dec. 31, 2013 Significant Other Observable Fair Value Inputs (Level 2) [Member] Auction Rate Securities [Member]	Sep. 30, 2014 Significant Other Observable Fair Value Inputs (Level 2) [Member] Swap [Member]	Dec. 31, 2013 Significant Other Observable Fair Value Inputs (Level 2) [Member] Swap [Member]	Sep. 30, 2014 Significant Other Observable Fair Value Inputs (Level 2) [Member] Commodity Option [Member]	Dec. 31, 2013 Significant Other Observable Fair Value Inputs (Level 2) [Member] Commodity Option [Member]	Sep. 30, 2014 Fair Value, Inputs, Level 3 [Member]	Dec. 31, 2013 Fair Value, Inputs, Level 3 [Member]	Sep. 30, 2014 Fair Value, Inputs, Level 3 [Member] Equity Securities [Member]	Dec. 31, 2013 Fair Value, Inputs, Level 3 [Member] Equity Securities [Member]	Dec. 31, 2013 Fair Value, Inputs, Level 3 [Member] Auction Rate Securities [Member]	Sep. 30, 2014 Fair Value, Inputs, Level 3 [Member] Swap [Member]	Dec. 31, 2013 Fair Value, Inputs, Level 3 [Member] Swap [Member]	Sep. 30, 2014 Fair Value, Inputs, Level 3 [Member] Commodity Option [Member]	Dec. 31, 2013 Fair Value, Inputs, Level 3 [Member] Commodity Option [Member]	Sep. 30, 2014 Investments [Member]	Sep. 30, 2013 Investments [Member]	Dec. 31, 2013 Investments [Member]	Dec. 31, 2012 Investments [Member]	Sep. 30, 2014 Derivative Financial Instruments, Assets [Member]	Sep. 30, 2013 Derivative Financial Instruments, Assets [Member]	Dec. 31, 2013 Derivative Financial Instruments, Assets [Member]	Dec. 31, 2012 Derivative Financial Instruments, Assets [Member]	Sep. 30, 2014 Stock Compensation Plan [Member]	Sep. 30, 2013 Stock Compensation Plan [Member]	Dec. 31, 2013 Stock Compensation Plan [Member]	Dec. 31, 2012 Stock Compensation Plan [Member]	Sep. 30, 2014 5.75% Senior Notes Due 2022 [Member]	Dec. 31, 2013 5.75% Senior Notes Due 2022 [Member]	Sep. 30, 2014 5.625% Senior Notes Due 2024 [Member]	Dec. 31, 2013 5.625% Senior Notes Due 2024 [Member]	Sep. 30, 2014 7.125% Senior Subordinated Notes due 2018 [Member]	Dec. 31, 2013 7.125% Senior Subordinated Notes due 2018 [Member]	Sep. 30, 2014 6.875% Senior Subordinated Notes due 2020 [Member]	Dec. 31, 2013 6.875% Senior Subordinated Notes due 2020 [Member]
Debt Instrument, Fair Value Disclosure																																																												$ 836	$ 767	$ 1,072	$ 1,025	$ 615	$ 624	$ 730	$ 755
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value						(8)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		41	26	151																																												0	39	39	36		10		115
Liability Value	8																																																			1		8		7	(8)	5	0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Investment Income		(16)																																														0	0				(8)				(8)
Fair Value, Liabilities Measured on Recurring Basis, Change in Unrealized Gain (Loss)	17																																																			20				(3)
Money Market Funds, at Carrying Value	365		2																		365	2								0	0								0	0
Deferred Compensation Plan Assets	9		8																		9	8								0	0								0	0
Fair Value Assumptions Expected Volatility Curves							52.12%	14.54%			50.03%	24.78%
Fair Value Inputs, Entity Credit Risk							3.95%	0.01%			0.639%	0.01%
Derivative Asset, Fair Value, Total					84				19	7
Available-for-sale Securities, Fair Value Disclosure													9	8		39							9	8	0							0	0	0							0	0	39
Derivative Assets																	(104)										0	0	0						(104)		0	0							0
Derivative Liability																		(28)	(1)	(8)						0										(28)								0		(1)	(8)
Assets, Fair Value Disclosure	466		5																		370	7								104										26
Financial and Nonfinancial Liabilities, Fair Value Disclosure																															(28)								(8)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	(42)	(67)																																														0	0				(59)				(8)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	(39)																																															(39)				0				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings																																																				0				(42)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		4																																															4				0				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		47																																														0	1				46				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0	0																																														0	0			0	0			0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	44																																																			4				40
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3	3	0																																														0	0			3	0			0	0
Obligations, Fair Value Disclosure	(20)		(16)																											0	0
Proceeds from Sale of Available-for-sale Securities															$ 39