Equity-Based Compensation - ARI Restricted Stock Awards and ARI RSUs (Detail) (USD $)	3 Months Ended		3 Months Ended		3 Months Ended
	Mar. 31, 2014 Ari Restricted Stock Units RSU [Member]	Dec. 31, 2013 Ari Restricted Stock Units RSU [Member]	Mar. 31, 2014 Ari Restricted Stock	Dec. 31, 2013 Ari Restricted Stock	Mar. 31, 2014 2007 Omnibus Equity Incentive Plan, Plan Grants Restricted Stock Units (RSUs)	Mar. 31, 2013 2007 Omnibus Equity Incentive Plan, Plan Grants Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted Stock Unit, Fair Value Price, Marketability Discount, No Distributions					35.20%	15.30%
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Restricted stock unvested, beginning balance	174,402	274,402	0	0
Restricted stock unvested, vested	(48,000)		0
Restricted stock unvested, vested to the company	(52,000)		0
Weighted average grant date fair value, beginning balance	$ 15.86
Weighted average grant date fair value, vested to employee of the company	$ 14.90
Weighted average grant date fair value, vested to the company	$ 14.85
Weighted average grant date fair value, ending balance	$ 16.42
Restricted stock vested, beginning balance	428,372
Restricted stock vested, vested to employee of the company	48,000
Restricted stock vested, vested to the company	52,000
Restricted stock vested, ending balance	528,372
Number of restricted stock outstanding, beginning balance	702,774
Number of restricted stock outstanding, ending balance	702,774