Equity (Details 2) (USD $)	12 Months Ended		0 Months Ended			12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 04, 2012 Consolidated properties property	Jan. 10, 2014 Portfolio of ten properties property Item	Jan. 10, 2014 Portfolio of ten properties Consolidated properties property	Dec. 31, 2013 7.5% Cumulative Redeemable Preferred Units	Dec. 31, 2012 7.5% Cumulative Redeemable Preferred Units
Redeemable preferred stock
Number of partner's interest acquired				1
Number of properties contained in a portfolio			2	10	7
Consideration transferred for partner's interests acquired				$ 113,300,000
Temporary equity stated dividend rate percentage						7.50%	7.50%
Other noncontrolling redeemable interests in properties	164,948,000	152,469,000
Limited partners' preferred interest in the Operating Partnership and other noncontrolling redeemable interests in properties	190,485,000	178,006,000
Temporary equity, shares authorized						260,000	260,000
Temporary equity, shares issued						255,373	255,373
Temporary equity, shares outstanding						255,373	255,373
Limited partners' preferred interest in the Operating Partnership						25,537,000	25,537,000
Cumulative quarterly distributions on preferred units (in dollars per share)						$ 7.50
Temporary equity redemption price (in dollars per share)						$ 100.00
Liquidation preference (in dollars per share)						$ 100.00
Number of Series of Units Classified Into Temporary Equity	1
Noncontrolling interests redeemable at amounts in excess of fair value	$ 0