Redeemable Partnership Units (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Redeemable Noncontrolling Interests Rollforward [Abstract]
Reedemable Noncontrolling Interest, Beginning Balance	$ 1,003,620	$ 944,152
Net income	8,564	23,916
Other comprehensive income	1,260	9,034
Distributions	(16,824)	(17,541)
Redemption of Class A units, at redemption value	(19,771)	(14,980)
Adjustments to carry redeemable Class A units at redemption value	227,338	29,393
Redemption of Series D-15 redeemable units		(36,900)
Other, net	16,771	3,914
Reedemable Noncontrolling Interest, Ending Balance	1,220,958	940,988
Redeemable Noncontrolling Interests Additional Disclosure [Abstract]
Redeemable Noncontrolling Interest, Equity, Common, Carrying Amount	1,219,958		1,002,620
Capital Unit, Class A [Member]
Redeemable Noncontrolling Interests Additional Disclosure [Abstract]
Redeemable Noncontrolling Interest, Equity, Common, Carrying Amount	1,219,958		1,002,620
Cumulative Redeemable Preferred Unit [Member]
Redeemable Noncontrolling Interests Additional Disclosure [Abstract]
Fair value of Series G convertible preferred units and Series D-13 cumulative redeemable preferred units	$ 55,097		$ 55,097