Fair Values Of Assets And Liabilities (Narrative) (Details) MMcf in Thousands	9 Months Ended
	Sep. 30, 2016 USD ($) MMcf	Dec. 31, 2015 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 7,496,428	$ 0
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	7,496,428
Fair value, assets		0
Fair value, liabilities		0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value, assets		0
Fair value, liabilities	$ 0	$ 0
Beluga River Unit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated useful life	18 years
Proved developed producing reserves | MMcf	27