Redeemable Noncontrolling Interests (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			3 Months Ended	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Mar. 31, 2013 Common Class A [Member]	Dec. 31, 2012 Common Class A [Member]
Redeemable Noncontrolling Interests Rollforward [Abstract]
Reedemable Noncontrolling Interest, Beginning Balance	$ 944,152	$ 1,160,677
Net income	14,719	19,145
Distributions	(8,946)	(12,236)
Conversion Of Class A Redeemable Units At Redemption Value	(13,404)	(13,028)
Adjustment to carry Class A redeemable units at redemption value	44,998	96,061
Cumulative Redeemable Preferred Units Redemption Amount				949,082	898,152
Other, net	(13,563)	(280)
Reedemable Noncontrolling Interest, Ending Balance	995,082	1,250,899
Redeemable Noncontrolling Interests Additional Disclosure [Abstract]
Redeemable Noncontrolling Interest, Equity, Common, Carrying Amount	949,082		898,152
Fair value of Series G convertible preferred units and Series D-13 cumulative redeemable preferred units	$ 55,097		$ 55,011