Noncontrolling Interest (Details) (USD $) In Millions, except Share data, unless otherwise specified		1 Months Ended		3 Months Ended	6 Months Ended			6 Months Ended
	Jun. 30, 2012 Operating Partnership	Jun. 30, 2012 Columbus Nova	Jun. 15, 2012 Columbus Nova	Jun. 30, 2012 Noncontrolling Common Units Operating Partnership	Jun. 30, 2012 Noncontrolling Common Units Operating Partnership	Apr. 20, 2011 Noncontrolling Common Units Operating Partnership	Jun. 30, 2012 LTIP Units Operating Partnership	Jun. 30, 2012 LTIP Units Operating Partnership 2011 Plan
Noncontrolling interest
Units held by noncontrolling interests (in shares)				6,981,857	6,981,857		408,206
Ownership interest held by noncontrolling owners (as a percent)	22.85%
Issue price of units (in dollars per share)						$ 13.00
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			1
Noncontrolling common units converted to common stock (in shares)				623,932
Number of shares of common stock received on redemption of noncontrolling common units				623,932
Number of common units of operating partnership issued		15,789
Fair value of common units of operating partnership issued			$ 0.2