Stockholders’ Equity and Earnings (Loss) Per Share (Narrative) (Details) (USD $)	1 Months Ended	3 Months Ended		9 Months Ended			3 Months Ended		9 Months Ended			0 Months Ended		1 Months Ended
	Aug. 31, 2012	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Jan. 04, 2011	Sep. 30, 2012 Class A Joint Venture Shares [Member]	Sep. 30, 2011 Class A Joint Venture Shares [Member]	Sep. 30, 2012 Class A Joint Venture Shares [Member]	Sep. 30, 2011 Class A Joint Venture Shares [Member]	Mar. 09, 2012 Class A [Member]	Sep. 30, 2011 Common Stock [Member]	Jan. 04, 2011 Common Stock [Member]	Aug. 31, 2012 Secondary Public Offering [Member] Common Stock [Member]	Aug. 31, 2012 Private Placement [Member] MGN (USA), Inc [Member] Common Stock [Member]	Aug. 31, 2012 Underwriter Options Exercised [Member] Common Stock [Member]
Schedule of Equity Method Investments [Line Items]
Issuance of common stock (in shares)														3,600,000	500,000	465,000
Issuance of common stock, price per share (in usd per share)														$ 21.20
Stock offering proceeds, net	$ 85,600,000			$ 86,490,000	$ 116,519,000
Stock issuance costs	813,000			813,000	1,150,000
Transferred outstanding promissory note						67,000,000
Transferred outstanding promissory note shares							11,400,000	1,400,000	1,400,000	1,400,000			4,100,000
Conversion of Class A share by LIH												10,000
Business acquisition, common shares sold by LIH											4,100,000
General and administrative expenses				$ 169,000
Common stock not included in the calculation of EPS, shares		1,900,000	1,900,000	1,900,000	1,900,000
Common stock price lower range limit (in usd per share)		$ 21.64			$ 18.88
Common stock price upper range limit (in usd per share)		$ 26.66			$ 26.66