Earnings Per Share - Common Shares Related to Stock Options and RSUs Excluded from Calculated Diluted Net Income Per Share (Parenthetical) (Detail)	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Dilutive Securities Included And Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Performance based options, bearing right to acquire common stock	210,000
Restricted stock units, bearing right to acquire common stock	254,000
Restricted Stock Units (RSUs) [Member]
Dilutive Securities Included And Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Restricted stock units, bearing right to acquire common stock		400,000
Restricted stock units, bearing right to acquire common stock	44,000