Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Parent Company [Member]
Net income	$ 21,134	$ 26,735
Other comprehensive income (loss):
Amortization of loss on settlement of derivative instruments recognized in net income	2,367	2,367
Effective portion of change in fair value of derivative instruments	3,372	(34)
Less: reclassification adjustment for change in fair value of derivative instruments included in net income	8	3
Other comprehensive income	5,747	2,336
Comprehensive income	26,881	29,071
Less: comprehensive income (loss) attributable to noncontrolling interests:
Net income (loss) attributable to noncontrolling interests	314	(383)
Other comprehensive income (loss) attributable to noncontrolling interests	15	(10)
Comprehensive income (loss) attributable to noncontrolling interests	329	(393)
Comprehensive income attributable to the Company/Partnership	26,552	29,464
Partnership Interest [Member]
Net income	21,134	26,735
Other comprehensive income (loss):
Amortization of loss on settlement of derivative instruments recognized in net income	2,367	2,367
Effective portion of change in fair value of derivative instruments	3,372	(34)
Less: reclassification adjustment for change in fair value of derivative instruments included in net income	8	3
Other comprehensive income	5,747	2,336
Comprehensive income	26,881	29,071
Less: comprehensive income (loss) attributable to noncontrolling interests:
Net income (loss) attributable to noncontrolling interests	275	192
Other comprehensive income (loss) attributable to noncontrolling interests	4	(15)
Comprehensive income (loss) attributable to noncontrolling interests	279	177
Comprehensive income attributable to the Company/Partnership	$ 26,602	$ 28,894