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Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Parenthetical) (Detail) (USD $)
3 Months Ended 6 Months Ended
Jun. 30, 2014
Jun. 30, 2013
Jun. 30, 2014
Jun. 30, 2013
Dec. 31, 2013
Jan. 30, 2013
Initial public offering [Member]
Class of Stock [Line Items]            
Antidilutive stock options excluded from calculation of diluted income per share 0 0 0 0    
Common stock shares issued at initial public offering 31,632,533   31,632,533   31,597,907 10,000,000
Common stock public offering price           $ 17.00