Stock-Based Compensation - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 EquityPlan	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity incentive plans	2
Plan with maximum term from the date of grant	10 years
Percentage of discount on purchase price of share with fair market value	15.00%
ESPP generally provides offering periods	6 months
Percentage of purchase price of share with fair market value	85.00%
Due to the timing of the IPO, the initial offering period under the ESPP period	8 months 15 days
Due to the timing of the IPO, the initial offering period under the ESPP	February 23, 2012 to November 15, 2012
Options granted become exercisable ratably over the vesting period	5 years
Total intrinsic value of options exercised	$ 19.6	$ 2.5	$ 3.4
Option outstanding weighted-average remaining contractual term	7 years
Option outstanding aggregate intrinsic value	47.9
Option exercisable weighted-average remaining contractual term	5 years 6 months
Option exercisable aggregate intrinsic value	26.9
Total unrecognized compensation expense related to unvested stock options	5.6
Total unrecognized compensation expense related to unvested stock options, expected to be recognized over a weighted average period	2 years 8 months 12 days
The total fair value of options vested	$ 1.3	$ 5.6	$ 1.2
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%	0.00%	0.00%
2012 Long-Term Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Plan with maximum term from the date of grant	10 years