Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Other comprehensive income:
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	$ (49,968)	$ 30,985	$ 4,220
Parent Company [Member]
Net income	188,847	151,285	26,209
Other comprehensive income:
Amortization of loss on derivative instruments	8,747	9,466	9,466
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	(49,968)	30,985	4,220
Less: reclassification adjustment for change in fair value of derivative instruments included in net income	606	(33)	25
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	7,765	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	(7,765)	0	0
Other comprehensive income	(40,615)	40,418	13,711
Comprehensive income	148,232	191,703	39,920
Less: comprehensive (loss) income attributable to noncontrolling interests:
Net income attributable to noncontrolling interests	1,457	1,481	342
Comprehensive income attributable to noncontrolling interests	1,186	1,588	339
Other Comprehensive (Income) Loss, Net of Tax, Portion Attributable to Noncontrolling Interest	(271)	107	(3)
Comprehensive income attributable to the Company	147,046	190,115	39,581
Partnership Interest [Member]
Net income	188,847	151,285	26,209
Other comprehensive income:
Unrealized loss on derivative instruments	0	0	0
Amortization of loss on derivative instruments	8,747	9,466	9,466
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	(49,968)	30,985	4,220
Less: reclassification adjustment for change in fair value of derivative instruments included in net income	606	(33)	25
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	7,765	0	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	(7,765)	0	0
Other comprehensive income	(40,615)	40,418	13,711
Comprehensive income	148,232	191,703	39,920
Less: comprehensive (loss) income attributable to noncontrolling interests:
Net income attributable to noncontrolling interests	1,138	1,205	865
Comprehensive income attributable to noncontrolling interests	937	1,237	834
Other Comprehensive (Income) Loss, Net of Tax, Portion Attributable to Noncontrolling Interest	(201)	32	(31)
Comprehensive income attributable to the Company	147,295	190,466	39,086
Noncontrolling Interests in Limited Partners Interest in Consolidated Partnerships [Member] | Parent Company [Member]
Net income	1,138	1,205	865
Other comprehensive income:
Other comprehensive income	$ (201)	$ 32	$ (31)