Fair Value Measurements and Derivative Instruments - Income Statement Hedging Instruments (Details) (Fair Value Hedging, USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 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	$ (15,579)	$ 790
Amount of Gain (Loss) Recognized in Income on Hedged Item	5,893	(10,688)
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	(3,069)	(779)
Amount of Gain (Loss) Recognized in Income on Hedged Item	(5,542)	(9,276)
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	(12,510)	1,569
Amount of Gain (Loss) Recognized in Income on Hedged Item	$ 11,435	$ (1,412)