Redeemable Partnership Units (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended			6 Months Ended	12 Months Ended	0 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 Capital Unit, Class A [Member]	Dec. 31, 2012 Capital Unit, Class A [Member]	May 09, 2013 Series D15 Cumulative Redeemable Preferred Unit [Member]	Jun. 30, 2013 Cumulative Redeemable Preferred Unit [Member]	Dec. 31, 2012 Cumulative Redeemable Preferred Unit [Member]
Redeemable Noncontrolling Interests Rollforward [Abstract]
Reedemable Noncontrolling Interest, Beginning Balance	$ 944,152	$ 1,160,677
Net income	23,916	24,355
Distributions	(17,541)	(24,457)
Redemption of Class A units, at redemption value	(14,980)	(24,976)
Adjustment to carry redeemable Class A units at redemption value	29,393	110,581
Redemption of Series D-15 redeemable units	(36,900)			939,988	898,152
Other, net	(12,948)	9,355
Reedemable Noncontrolling Interest, Ending Balance	940,988	1,236,825
Redeemable Noncontrolling Interests Additional Disclosure [Abstract]
Redeemable Noncontrolling Interest, Equity, Common, Carrying Amount	939,988		898,152
Temporary Equity Dividend Rate Percentage						6.875%
Fair value of Series G convertible preferred units and Series D-13 cumulative redeemable preferred units							55,073	55,011
Aggregate face amount of Cumulative redeemable preferred units						45,000
Redemption of Series D-15 redeemable units	$ (36,900)			$ 939,988	$ 898,152