Equity - Reclassifications Out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss)
Beginning equity balance, value	$ 2,343,257	$ 2,315,004
Amounts reclassified from accumulated other comprehensive loss to:
Interest expense	20,550	23,390
Total other comprehensive loss	24,603	6,086
Ending equity balance, value	2,362,297	2,322,607
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss)
Beginning equity balance, value	(78,420)	(156,676)
Amounts reclassified from accumulated other comprehensive loss to:
Ending equity balance, value	(54,364)	(150,849)
Gains and Losses on Derivative Instruments
Accumulated Other Comprehensive Income (Loss)
Beginning equity balance, value	9,087	29,549
Amounts reclassified from accumulated other comprehensive loss to:
Ending equity balance, value	6,755	26,996
Gains and Losses on Marketable Securities
Accumulated Other Comprehensive Income (Loss)
Beginning equity balance, value	(15)	(48)
Amounts reclassified from accumulated other comprehensive loss to:
Ending equity balance, value	(15)	(18)
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss)
Beginning equity balance, value	(87,492)	(186,177)
Amounts reclassified from accumulated other comprehensive loss to:
Ending equity balance, value	(61,104)	(177,827)
AOCI Including Portion Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income (Loss)
Other comprehensive loss before reclassifications	25,659	8,238
Amounts reclassified from accumulated other comprehensive loss to:
Total	(1,056)	(2,152)
Total other comprehensive loss	24,603	6,086
AOCI Including Portion Attributable to Noncontrolling Interest | Reclassification out of Accumulated Other Comprehensive Income
Amounts reclassified from accumulated other comprehensive loss to:
Interest expense	436	706
Other income and (expenses)	(1,492)	(2,858)
Gains and Losses on Derivative Instruments
Accumulated Other Comprehensive Income (Loss)
Other comprehensive loss before reclassifications	(1,276)	(401)
Amounts reclassified from accumulated other comprehensive loss to:
Total	(1,056)	(2,152)
Total other comprehensive loss	(2,332)	(2,553)
Gains and Losses on Derivative Instruments | Reclassification out of Accumulated Other Comprehensive Income
Amounts reclassified from accumulated other comprehensive loss to:
Interest expense	436	706
Other income and (expenses)	(1,492)	(2,858)
Gains and Losses on Marketable Investments
Accumulated Other Comprehensive Income (Loss)
Other comprehensive loss before reclassifications	0	30
Amounts reclassified from accumulated other comprehensive loss to:
Total	0	0
Total other comprehensive loss	0	30
Gains and Losses on Marketable Investments | Reclassification out of Accumulated Other Comprehensive Income
Amounts reclassified from accumulated other comprehensive loss to:
Interest expense	0	0
Other income and (expenses)	0	0
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss)
Other comprehensive loss before reclassifications	26,935	8,609
Amounts reclassified from accumulated other comprehensive loss to:
Total	0	0
Total other comprehensive loss	26,935	8,609
Foreign Currency Translation Adjustments | Reclassification out of Accumulated Other Comprehensive Income
Amounts reclassified from accumulated other comprehensive loss to:
Interest expense	0	0
Other income and (expenses)	0	0
Noncontrolling Interests
Amounts reclassified from accumulated other comprehensive loss to:
Net current-period Other comprehensive income attributable to noncontrolling interests	(547)	(259)
Gains and Losses on Derivative Instruments
Amounts reclassified from accumulated other comprehensive loss to:
Net current-period Other comprehensive income attributable to noncontrolling interests	0	0
Gains and Losses on Marketable Securities
Amounts reclassified from accumulated other comprehensive loss to:
Net current-period Other comprehensive income attributable to noncontrolling interests	0	0
Foreign Currency Translation Adjustments
Amounts reclassified from accumulated other comprehensive loss to:
Net current-period Other comprehensive income attributable to noncontrolling interests	$ (547)	$ (259)