Equity - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Equity [Line Items]
Shares absorbed into plan	5,700
Term of plan, in years	10 years
Weighted average remaining contractual term option outstanding	4 years 4 months
Weighted average remaining contractual term option exercisable	3 years 2 months
Shares available for future grants	10,400	11,600	6,800
Total pre-tax intrinsic value of stock options exercised	$ 1.4	$ 3.3
Total pre-tax intrinsic value based on the closing stock price	$ 13.27
Intrinsic value of stock options outstanding	$ 5.9
Intrinsic value of stock options exercisable	$ 4.0
Weighted average remaining contractual term for unvested restricted shares, in years	2 years 4 months	2 years 4 months
performance shares granted	200
Share-based payment awards in the form of stock option awards	411	651	553
Contractual term of stock options (in years)	7 years
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	2 years 6 months
Minimum
Equity [Line Items]
Vesting period, in years	3 years
Maximum
Equity [Line Items]
Vesting period, in years	4 years
Unvested Stock Options
Equity [Line Items]
Total compensation cost not yet recognized	$ 3.2
Restricted Stock
Equity [Line Items]
Total compensation cost not yet recognized		$ 17.6
Employee Stock Purchase Plan
Equity [Line Items]
Shares available for future grants	600
Percentage of employee contribution from compensation	10.00%
Rate of discount from the fair market value	15.00%
Shares purchase by employees	300	200	200
Weighted-average price per share paid by the employees	$ 11.21	$ 10.57	$ 8.00