Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance		$ 3,148,366
Ending Balance		3,197,225
Total accumulated other comprehensive loss		3,148,366		$ 3,197,225	$ 3,148,366
Total accumulated other comprehensive loss included in shareholders' equity/owners' equity				3,134,884	3,087,358
Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance		(38,701)	$ (56,767)
Unrealized income (loss)		(6,206)	10,680
Ending Balance		(44,907)	(46,087)
Total accumulated other comprehensive loss		(38,701)	(56,767)	(44,907)	(38,701)	$ (46,087)
Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance		150	(455)
Unrealized income (loss)		425	(41)
Reclassification adjustment	[1]	62	316
Ending Balance		637	(180)
Total accumulated other comprehensive loss		150	(455)	637	150	(180)
AOCI Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Ending Balance		(44,270)	(46,267)
Total accumulated other comprehensive loss		(44,270)	(46,267)	(44,270)		(46,267)
AOCI Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Ending Balance		887	935
Total accumulated other comprehensive loss		887	$ 935	887		935
AOCI Attributable to Parent [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance		(37,797)
Ending Balance		(43,383)
Total accumulated other comprehensive loss		$ (37,797)		(43,383)	$ (37,797)
Total accumulated other comprehensive loss included in shareholders' equity/owners' equity				$ (43,383)		$ (45,332)

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