Permanent and Temporary Equity (Redeemable OP Unitholder and Noncontrolling Interest) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Temporary Equity [Line Items]
Balance as of December 31, 2013	$ 156,660
New issuances	20,643
Change in valuation	29,042
Distributions and other	(7,739)
Redemptions	(26,590)
Balance as of December 31, 2014	172,016
Redeemable Noncontrolling Interests
Temporary Equity [Line Items]
Balance as of December 31, 2013	45,053
New issuances	0
Change in valuation	(4,020)
Distributions and other	(1,982)
Redemptions	(26,169)
Balance as of December 31, 2014	12,882
Redeemable OP Unitholder Interests
Temporary Equity [Line Items]
Balance as of December 31, 2013	111,607
New issuances	20,643
Change in valuation	33,062
Distributions and other	(5,757)
Redemptions	(421)
Balance as of December 31, 2014	$ 159,134