Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Parent Company [Member]
Net income	$ 11,348	$ 18,937	$ 38,083	$ 27,067
Other comprehensive income (loss):
Amortization of loss on settlement of derivative instruments recognized in net income	2,366	2,366	4,733	4,733
Effective portion of change in fair value of derivative instruments	(26)	0	(60)	0
Less reclassification adjustment for change in fair value of derivative instruments included in net income	7	0	9	0
Other comprehensive income	2,347	2,366	4,682	4,733
Comprehensive income	13,695	21,303	42,765	31,800
Less: comprehensive income (loss) attributable to noncontrolling interests:
Net (loss) income attributable to noncontrolling interests	255	1,157	(128)	2,183
Other comprehensive (loss) income attributable to noncontrolling interests	(6)	5	(16)	10
Comprehensive income (loss) attributable to noncontrolling interests	249	1,162	(144)	2,193
Comprehensive income attributable to the Company/Partnership	13,446	20,141	42,909	29,607
Partnership Interest [Member]
Net income	11,348	18,937	38,083	27,067
Other comprehensive income (loss):
Amortization of loss on settlement of derivative instruments recognized in net income	2,366	2,366	4,733	4,733
Effective portion of change in fair value of derivative instruments	(26)	0	(60)	0
Less reclassification adjustment for change in fair value of derivative instruments included in net income	7	0	9	0
Other comprehensive income	2,347	2,366	4,682	4,733
Comprehensive income	13,695	21,303	42,765	31,800
Less: comprehensive income (loss) attributable to noncontrolling interests:
Net (loss) income attributable to noncontrolling interests	232	189	424	271
Other comprehensive (loss) income attributable to noncontrolling interests	(10)	0	(25)	0
Comprehensive income (loss) attributable to noncontrolling interests	222	189	399	271
Comprehensive income attributable to the Company/Partnership	13,473	21,114	42,366	31,529
Limited Partners [Member] | Partnership Interest [Member]
Net income			77	50
Other comprehensive income (loss):
Other comprehensive income			$ 9	$ 10