Earnings per Share (Summary of Basic and Diluted Earnings per Share Footnote) (Details)	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted average shares outstanding-diluted	39,209,226	[1]	36,889,474	[1]
Class A Units [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted average shares outstanding-diluted	7,317,000		7,797,000
Class O Units [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted average shares outstanding-diluted	436,000		24,000
Class RS Units [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted average shares outstanding-diluted	7,317,000		7,797,000
Options to purchase Class A common stock [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted average shares outstanding-diluted	216,000		52,000

[1] Includes 7,317 Class A and Class RS units, 436 “in the money” value of Class O units on an “as if” converted basis and 216 “in the money” value options to purchase shares of Class A common stock on an “as if” converted basis as of the three months ended March 31, 2015. As of the three months ended March 31, 2014, this amount includes 7,797 Class A and Class RS units, 24 “in the money” value of Class O units on as “as if” converted basis and 52 “in the money” value options to purchase shares of Class A common stock on an “as if” converted basis.