Other Comprehensive Income (Loss) Other Comprehensive Income Balance Components (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Unrealized gain on post-retirement benefit obligations	$ 20,737	$ 20,737
Unrealized gain (loss) on marketable securities	0	(61)
Unrealized gain (loss) on hedging activities, net of noncontrolling interest	(25,303)	(24,831)
Accumulated other comprehensive income	$ (4,566)	$ (4,155)