Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance		$ 3,086,377
Ending Balance		3,007,109
Total accumulated other comprehensive (loss) income		3,086,377		$ 3,007,109	$ 3,086,377
Total accumulated other comprehensive (loss) income included in shareholders' equity/owners' equity				2,950,221	3,027,672
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		(5,823)	$ 8,592
Other comprehensive income (loss), before reclassifications		(6,229)	(5,189)
Ending Balance		(12,052)	3,403
Total accumulated other comprehensive (loss) income		(5,823)	8,592	(12,052)	(5,823)	$ 3,403
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		(377)	1,584
Other comprehensive income (loss), before reclassifications		(2,592)	(2,090)
Reclassification adjustment	[1]	1,053	1,100
Ending Balance		(1,916)	594
Total accumulated other comprehensive (loss) income		(377)	1,584	(1,916)	(377)	594
AOCI Including Portion Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Ending Balance		(13,968)	3,997
Total accumulated other comprehensive (loss) income		(13,968)	3,997	(13,968)		3,997
AOCI Attributable to Noncontrolling Interest [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Ending Balance		131	(290)
Total accumulated other comprehensive (loss) income		131	$ (290)	131		(290)
AOCI Attributable to Parent [Member]
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance		(6,252)
Ending Balance		(13,837)
Total accumulated other comprehensive (loss) income		$ (6,252)		(13,837)	$ (6,252)
Total accumulated other comprehensive (loss) income included in shareholders' equity/owners' equity				$ (13,837)		$ 3,707

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