Noncontrolling Interest (Details)	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Noncontrolling interest
Noncontrolling common units converted to common stock (in shares)	0
Operating Partnership
Noncontrolling interest
Ownership interest held by noncontrolling owners (as a percent)	13.06%	14.71%
Noncontrolling Common Units | Operating Partnership
Noncontrolling interest
Units held by noncontrolling interests (in shares)	5,743,958	5,743,958
Redemption right of investor to cause the Operating Partnership to redeem its units equivalent to current market value of number of shares of entity's common stock (in shares)	1
Conversion ratio of noncontrolling units	1
LTIP Units | Operating Partnership
Noncontrolling interest
Units held by noncontrolling interests (in shares)	601,120	413,551
LTIP Units | Operating Partnership | 2011 Plan
Noncontrolling interest
Conversion ratio of noncontrolling units	1