Accumulated Other Comprehensive Loss - (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2014
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning Balance		$ 3,062,923	$ 3,030,254
Ending Balance		3,148,366	3,062,923
Total equity		3,062,923	3,030,254	$ 3,148,366	$ 3,062,923	$ 3,106,312
Total accumulated other comprehensive loss included in shareholders' equity				3,087,358	3,003,391
Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning Balance		(56,767)	(22,023)
Other comprehensive income (loss), before reclassifications		18,066	(34,744)
Ending Balance		(38,701)	(56,767)
Total equity		(56,767)	(22,023)	(38,701)	(56,767)
Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning Balance		(455)	(865)
Other comprehensive income (loss), before reclassifications		152	(659)
Reclassification adjustment	[1]	453	1,069
Ending Balance		150	(455)
Total equity		(455)	(865)	150	(455)
AOCI Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning Balance		(57,222)
Ending Balance		(38,551)	(57,222)
Total equity		(57,222)	(57,222)	(38,551)	(57,222)
AOCI Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning Balance		1,191
Ending Balance		754	1,191
Total equity		1,191	1,191	754	1,191
AOCI Attributable to Parent [Member]
AOCI Including Portion Attributable to Noncontrolling Interest [Abstract]
Beginning Balance		(56,031)	(22,506)
Ending Balance		(37,797)	(56,031)
Total equity		$ (56,031)	$ (22,506)	(37,797)	(56,031)	$ (9,784)
Total accumulated other comprehensive loss included in shareholders' equity				$ (37,797)	$ (56,031)

[1] (1)Amounts reclassified out of Accumulated Other Comprehensive Loss/General & Limited Partner's Equity into contractual interest expense.