Stock Based Compensation - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	9 Months Ended						36 Months Ended			9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Employee Stock Option	Sep. 30, 2014 Restricted Stock	Sep. 30, 2014 Restricted Stock Units (RSUs)	Sep. 30, 2014 Performance Shares	Dec. 31, 2016 Performance Shares Scenario Forecast	Dec. 31, 2015 Performance Shares Scenario Forecast	Dec. 31, 2014 Performance Shares Scenario Forecast	Sep. 30, 2014 Performance Shares Minimum	Sep. 30, 2014 Performance Shares Maximum	Sep. 30, 2014 Plan 2011	Sep. 30, 2014 Plan 2011 Employee Stock Option	Sep. 30, 2014 Directors Plan	Sep. 30, 2014 Directors Plan Restricted Stock	Sep. 30, 2014 Plan 2000 Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Plan term, years												10 years	10 years			10 years
Share based compensation arrangement plan expiration														Oct. 31, 2016
Shares authorized for grants												3,800,000
Unamortized compensation expense expected to be vested	$ 27.7
Recognized weighted average period, years	1 year 2 months 12 days
Stock-based compensation expense	$ 19.1	$ 17.6	$ 1.8	$ 4.5	$ 1.8	$ 10.3								$ 0.7
Vesting period, maximum years													4 years		1 year	4 years
Performance goal period to vest incentive stock awards						3 years
Percentage of Incentive Stock Awards Expected to be Vested and Awarded of Stocks Granted							100.00%	104.00%	180.00%	0.00%	200.00%