Equity (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss)
Beginning balance	$ (13,442)	$ (41,599)	$ (38,150)
Other comprehensive income (loss) before reclassifications	(74,751)	22,571	(7,120)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	6,074	6,333	4,227
Net current-period Other comprehensive income (loss)	(68,677)	28,904	(2,893)
Net current-period Other comprehensive (income) loss attributable to noncontrolling interests	1,112	(747)	(556)
Ending balance	(81,007)	(13,442)	(41,599)
Interest Expense
Accumulated Other Comprehensive Income (Loss)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	7,970	8,457	5,757
Other income and expense
Accumulated Other Comprehensive Income (Loss)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(1,896)	(2,124)	(1,530)
Gains and Losses on Derivative Instruments
Accumulated Other Comprehensive Income (Loss)
Beginning balance	(16,717)	(19,250)	(3,141)
Other comprehensive income (loss) before reclassifications	18,365	(3,265)	(19,217)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	6,074	6,333	3,473
Net current-period Other comprehensive income (loss)	24,439	3,068	(15,744)
Net current-period Other comprehensive (income) loss attributable to noncontrolling interests	(411)	(535)	(365)
Ending balance	7,311	(16,717)	(19,250)
Gains and Losses on Derivative Instruments | Interest Expense
Accumulated Other Comprehensive Income (Loss)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	7,970	8,457	5,757
Gains and Losses on Derivative Instruments | Other income and expense
Accumulated Other Comprehensive Income (Loss)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	(1,896)	(2,124)	(2,284)
Gains and Losses on Marketable Securities
Accumulated Other Comprehensive Income (Loss)
Beginning balance	(391)	(485)	(1,520)
Other comprehensive income (loss) before reclassifications	285	94	281
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0	754
Net current-period Other comprehensive income (loss)	285	94	1,035
Net current-period Other comprehensive (income) loss attributable to noncontrolling interests	0	0	0
Ending balance	(106)	(391)	(485)
Gains and Losses on Marketable Securities | Interest Expense
Accumulated Other Comprehensive Income (Loss)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0	0
Gains and Losses on Marketable Securities | Other income and expense
Accumulated Other Comprehensive Income (Loss)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0	754
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss)
Beginning balance	3,666	(21,864)	(33,489)
Other comprehensive income (loss) before reclassifications	(93,401)	25,742	11,816
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0	0
Net current-period Other comprehensive income (loss)	(93,401)	25,742	11,816
Net current-period Other comprehensive (income) loss attributable to noncontrolling interests	1,523	(212)	(191)
Ending balance	(88,212)	3,666	(21,864)
Foreign Currency Translation Adjustments | Interest Expense
Accumulated Other Comprehensive Income (Loss)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0	0	0
Foreign Currency Translation Adjustments | Other income and expense
Accumulated Other Comprehensive Income (Loss)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ 0	$ 0	$ 0