Stock Compensation - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended				1 Months Ended				12 Months Ended					1 Months Ended		12 Months Ended				1 Months Ended
	Dec. 31, 2013	Dec. 31, 2013 Stock options	Dec. 31, 2013 Stock options Minimum	Dec. 31, 2013 Stock options Maximum	Jul. 31, 2013 Performance share units	Mar. 31, 2012 Performance share units	Apr. 30, 2011 Performance share units	Dec. 31, 2013 Performance share units	Dec. 31, 2013 Performance Shares 2013 Awards	Dec. 31, 2013 Stock and stock units	Dec. 31, 2012 Stock and stock units	Dec. 31, 2011 Stock and stock units	Dec. 31, 2013 Restricted shares or units	Jun. 30, 2009 Employee Stock Purchase Plan	Jun. 30, 2008 Employee Stock Purchase Plan	Dec. 31, 2013 Employee Stock Purchase Plan	Dec. 31, 2012 Employee Stock Purchase Plan	Dec. 31, 2011 Employee Stock Purchase Plan	Dec. 31, 1997 Employee Stock Purchase Plan	Jun. 30, 2008 Employee Stock Purchase Plan Minimum	Dec. 31, 2013 Stock Option Plan, 2006
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, vesting period			3 years	4 years		2 years	1 year
Stock options, expiration period		10 years
Shares available for awards under the plan																					8,079,200
Reserved common stock for issuance under the plan																			500,000
Additional shares of common stock reserved														750,000	500,000
Purchase price of common stock by employees																				85.00%
Payroll withholding period for purchase of shares of common stock															3 months
Shares of common stock issued under the plan																101,300	66,531	87,331
Stock options remaining contractual term	10 years
Total unrecognized compensation cost related to non vested stock options outstanding	$ 39.0
Weighted average period of compensation cost expected to be recognized		2 years 7 months 6 days											1 year 10 months 24 days
Total fair value of stock and stock unit awards vested										25.5	27.8	8.0
Unrecognized compensation expense													$ 18.6
Number of performance share units						258,400	173,500	333,000		2,047,600	1,903,445
Number of performance share units vested in period					274,400					1,444,307
Vesting date							2013-12
Percentage of Compensation Expense									60.00%