Fair Value Measurements and Derivative Instruments (Details 8) (Fair Value Hedging, USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Effect of derivative instruments involved in fair value hedging on the consolidated financial statements
Amount of Gain (Loss) Recognized in Income on Derivative	$ 10,839	$ 11,767	$ 11,278	$ 33,156
Amount of Gain (Loss) Recognized in Income on Hedged Item	1,491	1,010	12,465	(9,169)
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	4,880	4,444	9,862	8,881
Amount of Gain (Loss) Recognized in Income on Hedged Item	7,107	7,971	14,367	15,594
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	5,959	7,333	1,416	1,374
Amount of Gain (Loss) Recognized in Income on Hedged Item	(5,616)	(6,933)	(1,902)	(1,043)
Foreign currency forward contracts | 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		(10)		22,901
Amount of Gain (Loss) Recognized in Income on Hedged Item		$ (28)		$ (23,720)