Basis of Presentation and Accounting Policies Deferred Gains (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2014
Deferred Gains	$ 129,349	$ 146,076	$ 135,909	$ 159,911
Increase (Decrease) in Deferred Charges	9,003	2,035
Amortization of Deferred Gains	2,850	0
Operating Expense [Member]
Amortization of Deferred Gains	11,467	11,273
Gain (Loss) on Asset Dispositions and Impairments, Net [Member]
Amortization of Deferred Gains	$ 1,246	$ 4,597