Fair Value Measurements (Details) - USD ($)		Jun. 30, 2016	Dec. 31, 2015
Financial Assets:
Financial Assets: Natural Gas Price Swaps			$ 0
Financial Liabilities:
Financial Liabilities: Natural Gas Price Swaps		$ 1,300,000
Debt Disclosure [Abstract]
Estimated Fair Value of Debt		7,418,000,000	6,524,000,000
Aggregate Principal Amount of Current and Long-Term Debt		6,990,000,000	6,390,000,000
Fair Value, Inputs, Level 1 [Member]
Financial Assets:
Financial Assets: Natural Gas Price Swaps			0
Financial Liabilities:
Financial Liabilities: Natural Gas Price Swaps		0
Fair Value, Inputs, Level 2 [Member]
Financial Assets:
Financial Assets: Natural Gas Price Swaps			0
Financial Liabilities:
Financial Liabilities: Natural Gas Price Swaps	[1]	1,000,000
Fair Value, Inputs, Level 3 [Member]
Financial Assets:
Financial Assets: Natural Gas Price Swaps			$ 0
Financial Liabilities:
Financial Liabilities: Natural Gas Price Swaps		$ 0

[1] Balance at June 30, 2016, included in "Current Liabilities - Liabilities From Price Risk Management Activities" on the Consolidated Balance Sheets.