Fair Value Measurements and Derivative Instruments - Income Statement Hedging Instruments (Details) - Fair Value Hedging - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Effect of derivative instruments involved in hedging on the consolidated financial statements
Amount of Gain (Loss) Recognized in Income on Derivative	$ (5,925)	$ 25,134	$ 34,667	$ 30,420
Amount of Gain (Loss) Recognized in Income on Hedged Item	7,423	(16,284)	(17,675)	(6,470)
Interest rate swaps | Interest expense, net of interest capitalized
Effect of derivative instruments involved in hedging on the consolidated financial statements
Amount of Gain (Loss) Recognized in Income on Derivative	1,737	2,793	6,075	8,640
Amount of Gain (Loss) Recognized in Income on Hedged Item	0	3,968	7,203	11,775
Interest rate swaps | Other income (expense)
Effect of derivative instruments involved in hedging on the consolidated financial statements
Amount of Gain (Loss) Recognized in Income on Derivative	(7,662)	22,341	28,592	21,780
Amount of Gain (Loss) Recognized in Income on Hedged Item	$ 7,423	$ (20,252)	$ (24,878)	$ (18,245)