Equity (Details Textual) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended	3 Months Ended	6 Months Ended
	Jan. 19, 2011	Jun. 30, 2012	Jun. 30, 2012 Installment Anniversary	Jun. 30, 2011	Jan. 19, 2012	Mar. 16, 2011
Equity (Textual) [Abstract]
Restricted stock granted			one-third
Performance period to which performance-based vesting is subject, years	3 years		3 years
Noncash compensation expense			$ 1.4	$ 1.2
Unrecognized compensation expense		$ 5.6	$ 5.6
Equity (Additional Textual) [Abstract]
Vesting installments of restricted shares			2
Noncontrolling common units		18,394,476	18,394,476
Shares of common stock			1,613
Common stock price per share	$ 20.50	$ 22.56	$ 22.56
Percentage of ownership interests classified as noncontrolling		32.00%	32.00%
Restricted stock awards ratable vesting periods (anniversaries)			4
Grant Shares Date					Jan. 19, 2012	Mar. 16, 2011
Weighted average unvested shares outstanding		626,274	626,771
Restricted stock [Member]
Equity (Textual) [Abstract]
Performance period to which performance-based vesting is subject, years			3 years