Fair Value Measurements and Derivative Instruments (Income Statement Hedging Instruments) (Details) (Fair Value Hedging, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Effect of derivative instruments involved in fair value hedging on the consolidated financial statements
Amount of Gain (Loss) Recognized in Income on Derivative	$ 54,747	$ (62,276)
Amount of Gain (Loss) Recognized in Income on Hedged Item	(16,901)	106,488
Interest rate swaps | Interest expense, net of interest capitalized
Effect of derivative instruments involved in fair value hedging on the consolidated financial statements
Amount of Gain (Loss) Recognized in Income on Derivative	12,217	9,354
Amount of Gain (Loss) Recognized in Income on Hedged Item	17,403	37,745
Interest rate swaps | Other income (expense)
Effect of derivative instruments involved in fair value hedging on the consolidated financial statements
Amount of Gain (Loss) Recognized in Income on Derivative	42,530	(71,630)
Amount of Gain (Loss) Recognized in Income on Hedged Item	$ (34,304)	$ 68,743