Stock-Based Compensation - Additional Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	9 Months Ended			9 Months Ended
	Sep. 30, 2011 Year Entity Investment	Dec. 31, 2010	Sep. 30, 2011 2003 Long-Term Incentive Plan	Sep. 30, 2011 Stock Appreciation Rights Year	Sep. 30, 2011 Restricted Stock Units	Sep. 30, 2011 Restricted Stock Units Service Based Awards	Sep. 30, 2011 Restricted Stock Units Performance Based Awards	Sep. 30, 2011 Common Stock Equivalents	Sep. 30, 2011 Employee Stock Option	Sep. 30, 2010 Employee Stock Option	Sep. 30, 2011 Employee Stock Purchase Plan	Sep. 30, 2010 Employee Stock Purchase Plan
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Common stock available for stock-based compensation awards			6.4
Common stock available for stock-based compensation awards, par value	$ 0.0005	$ 0.0005	$ 0.0005
Vest ratably over				4 years		4 years	4 years
Total unrecognized stock-based compensation cost	$ 49.6
Expiration date				7 years
Total unrecognized stock-based compensation cost, period to be recognized	2.2			4
Share entitlement description					each RSU that vests entitles the awardee to one common share			each CSE entitles the holder to one common share
Directors' fees payable, percentage Board of Directors members can opt to receive in cash								50.00%
Cash received from option exercises									15.2	17.2
Percentage of employee's compensation, eligible employees may not exceed, when purchasing Common Stock through payroll deductions											10.00%
Amount of employee's compensation, eligible employees may not exceed, when purchasing Common Stock through payroll deductions											23,750
Price equals to closing price of Common Stock, percentage											95.00%
Shares available for purchase											1.4
Cash received from share purchases											$ 2.6	$ 2.2