Equity-Based Compensation - ARI Restricted Stock Awards and ARI RSUs (Detail) (USD $)	6 Months Ended
	Jun. 30, 2013
Ari Restricted Stock Units RSU [Member]
Activity for ARI RSUs
Restricted stock unvested, beginning balance	237,542
Restricted stock unvested, granted	195,000
Restricted Stock Unvested, granted to the Company	40,000
Restricted stock unvested, forfeited	(5,000)
Restricted stock unvested, vested	(49,249)
Restricted stock unvested, vested to the company	(52,000)
Restricted stock unvested, ending balance	366,293
Weighted average grant date fair value, beginning balance	$ 14.62
Weighted average grant date fair value, granted	$ 16.66
Weighted average grant date fair value, granted to the company	$ 17.59
Weighted average grant date fair value, forfeited	$ 16.66
Weighted average grant date fair value, vested to employee of the company	$ 14.93
Weighted average grant date fair value, vested to the company	$ 14.85
Weighted average grant date fair value, ending balance	$ 15.93
Restricted stock vested, beginning balance	225,232
Restricted stock vested, granted
Restricted stock vested, granted to the company
Restricted stock vested, forfeited
Restricted stock vested, vested to employee of the company	49,249
Restricted stock vested, vested to the company	52,000
Restricted stock vested, ending balance	326,481
Number of restricted stock outstanding, beginning balance	462,774
Number of restricted stock outstanding, granted	195,000
Number of restricted stock outstanding, granted to the company	40,000
Number of restricted stock outstanding, forfeited	(5,000)
Number of restricted stock outstanding, vested to employee of the company
Number of restricted stock outstanding, vested to the company
Number of restricted stock outstanding, ending balance	692,774
Ari Restricted Stock [Member]
Activity for ARI RSUs
Restricted stock unvested, beginning balance
Restricted stock unvested, granted
Restricted Stock Unvested, granted to the Company
Restricted stock unvested, forfeited
Restricted stock unvested, vested
Restricted stock unvested, vested to the company
Restricted stock unvested, ending balance