Redeemable Partnership Units (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Redeemable Noncontrolling Interest Units Table [Abstract]
Redeemable Noncontrolling Interest, Equity, Common, Carrying Amount	$ 1,240,069		$ 1,223,793
Redeemable Noncontrolling Interests Rollforward [Abstract]
Reedemable Noncontrolling Interest, Balance At December 31	1,229,221	$ 1,337,780
Net income	7,044	15,485
Other comprehensive income (loss)	1,685	(2,635)
Distributions	(15,763)	(14,734)
Other, net	21,149	25,370
Reedemable Noncontrolling Interest, Balance At June 30	1,245,497	1,092,894
Common Class A [Member]
Redeemable Noncontrolling Interest Units Table [Abstract]
Redeemable Noncontrolling Interest, Equity, Common, Carrying Amount	1,240,069		1,223,793
Redeemable Noncontrolling Interests Rollforward [Abstract]
Redemption of Class A units, at redemption value	(18,208)	(43,278)
Adjustments to carry redeemable Class A units at redemption value	20,369	(229,521)
Series D17 Cumulative Redeemable Preferred Unit [Member]
Redeemable Noncontrolling Interests Rollforward [Abstract]
Issuance of Series D-17 Preferred Units		$ 4,427
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	$ 50,561		$ 50,561