Non-controlling Interest - Additional Information (Detail) (USD $)	3 Months Ended			1 Months Ended
	Mar. 31, 2015		Mar. 31, 2014	Apr. 30, 2015	Dec. 31, 2014	May 07, 2015	Oct. 07, 2013
Minority Interest [Line Items]
Exercise of stock options, Shares	263,568	[1]
Distributions for Taxes, non-controlling unitholders	$ 65,000		$ 2,552,000
Other Distributions, non-controlling unitholders	0		0
Distribution declaration date	May 07, 2015
Distribution payable date	Jun. 04, 2015
Tax benefit from tax receivable agreements	67,418,000
Current portion of payable to related parties pursuant to tax receivable agreements	3,914,000				3,914,000
Amounts paid to related parties pursuant to Tax Receivable Agreements (TRAs)	0		0
Subsequent Event
Minority Interest [Line Items]
Other Distributions, non-controlling unitholders				30,830,000
Distributions declared to non-controlling unitholders						2,217,000
RMCO, LLC
Minority Interest [Line Items]
Percentage of common membership units in subsidiaries	40.42%				39.89%		39.56%
RMCO, LLC | Non-controlling interest
Minority Interest [Line Items]
Total percentage of common stock units	59.58%				60.11%
Common Class A
Minority Interest [Line Items]
Exercise of stock options, Shares	263,568
Distributions declared to non-controlling unitholders	$ 2,217,000

[1] Cash received from stock option exercises for the three months ended March 31, 2015 was $937,000. The Company recorded a corporate income tax benefit relating to the options exercised during the three months ended March 31, 2015 of $1,105,000 in “Additional paid-in capital” in the accompanying Condensed Consolidated Balance Sheets and Condensed Consolidated Statement of Stockholders’ Equity.