Redeemable Partnership Units (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Redeemable Noncontrolling Interest Units Table [Abstract]
Redeemable Noncontrolling Interest, Equity, Common, Carrying Amount	$ 898,152	$ 934,677
Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount	46,000	226,000
Redeemable Noncontrolling Interests Rollforward [Abstract]
Balance at December 31,	1,160,677	1,327,974
Net income	(45,263)	(55,912)
Distributions	(54,315)	(50,865)
Conversion of Class A redeemable units into common shares, at redemption value	(89,762)	(64,830)
Adjustment to carry Class A redeemable units at redemption value	52,117	(98,092)
Cumulative Redeemable Preferred Units Redemption Amount	(168,300)	(28,000)
Other, net	(1,528)	18,578
Balance at December 31,	944,152	1,160,677
Redeemable Noncontrolling Interests Additional Disclosure [Abstract]
Fair value of Series G convertible preferred units and Series D-13 cumulative redeemable preferred units	55,011	54,865
Cumulative Redeemable Preferred Units Redemption Amount	168,300	28,000
Common Class A [Member]
Redeemable Noncontrolling Interest Units Table [Abstract]
Outstanding Partnership Units held by Third Parties	11,215,682	12,160,771
Preferred Or Annual Distribution Rate (in dollars per unit)	$ 2.76
Series D10 Cumulative Redeemable Preferred Unit [Member]
Redeemable Noncontrolling Interest Units Table [Abstract]
Dividend Percentage	7.00%
Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount	0	80,000
Outstanding Partnership Units held by Third Parties	0	3,200,000
Par or Stated Value Per Unit	$ 25.00
Preferred Or Annual Distribution Rate (in dollars per unit)	$ 1.75
Series D11 Cumulative Redeemable Preferred Unit [Member]
Redeemable Noncontrolling Interests Rollforward [Abstract]
Cumulative Redeemable Preferred Units Redemption Amount	(28,000)
Redeemable Noncontrolling Interests Additional Disclosure [Abstract]
Cumulative Redeemable Preferred Units Redemption Amount	28,000
Series D14 Cumulative Redeemable Preferred Unit [Member]
Redeemable Noncontrolling Interest Units Table [Abstract]
Dividend Percentage	6.75%
Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount	0	100,000
Outstanding Partnership Units held by Third Parties	0	4,000,000
Par or Stated Value Per Unit	$ 25.00
Preferred Or Annual Distribution Rate (in dollars per unit)	$ 1.6875
Series D15 Cumulative Redeemable Preferred Unit [Member]
Redeemable Noncontrolling Interest Units Table [Abstract]
Dividend Percentage	6.875%
Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount	45,000	45,000
Outstanding Partnership Units held by Third Parties	1,800,000	1,800,000
Par or Stated Value Per Unit	$ 25.00
Preferred Or Annual Distribution Rate (in dollars per unit)	$ 1.71875
Series D16 Cumulative Redeemable Preferred Unit [Member]
Redeemable Noncontrolling Interest Units Table [Abstract]
Dividend Percentage	5.00%
Redeemable Noncontrolling Interest, Equity, Preferred, Carrying Amount	$ 1,000	$ 1,000
Outstanding Partnership Units held by Third Parties	1	1
Par or Stated Value Per Unit	$ 1,000,000
Preferred Or Annual Distribution Rate (in dollars per unit)	$ 50,000
Cumulative Redeemable Preferred Unit [Member]
Redeemable Noncontrolling Interest Units Table [Abstract]
Outstanding Partnership Units held by Third Parties	1,800,001	9,000,001