Net Income Per Share - Additional Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Purchased Restricted Stock outstanding as percentage of common stock	0.70%	0.70%
Net income allocated to PRS	$ 0.7	$ 0.6
Maximum [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Difference amount between basic and diluted net income per share	$ 0.01	$ 0.01