Stock-Based Compensation (Detail) (USD $)	12 Months Ended				24 Months Ended	12 Months Ended									12 Months Ended			12 Months Ended							12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Retirement Eligible Employees Equity Award [Member]	Dec. 31, 2012 Retirement Eligible Employees Equity Award [Member]	Dec. 31, 2012 Stock Appreciation Rights (SARs) [Member]		Dec. 31, 2011 Stock Appreciation Rights (SARs) [Member]	Dec. 31, 2010 Stock Appreciation Rights (SARs) [Member]	Dec. 31, 2012 Restricted Stock Units (RSUs) [Member] Service Based Awards [Member]	Dec. 31, 2012 Restricted Stock Units (RSUs) [Member] Performance Shares [Member]	Dec. 31, 2012 Restricted Stock Units (RSUs) [Member]		Dec. 31, 2011 Restricted Stock Units (RSUs) [Member]	Dec. 31, 2012 Performance Shares [Member] Executive Officer [Member]	Dec. 31, 2012 Common Stock Equivalents [Member]	Dec. 31, 2011 Common Stock Equivalents [Member]	Dec. 31, 2012 Employee Stock Option [Member]	Dec. 31, 2011 Employee Stock Option [Member]	Dec. 31, 2012 Non Executive [Member] Service Based Awards [Member]	Dec. 31, 2012 Target Amount [Member] Minimum [Member]	Dec. 31, 2012 Target Amount [Member] Maximum [Member]	Dec. 31, 2012 Target Amount [Member] Performance Shares [Member]	Dec. 31, 2012 Unvested [Member]	Dec. 31, 2012 Employee Stock Purchase Plan [Member]	Dec. 31, 2011 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in Shares)	6,400,000
Share-based Compensation	$ 36,378,000	$ 32,865,000	$ 32,634,000	$ 5,100,000	$ 3,100,000	$ 6,400,000		$ 4,400,000	$ 4,600,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	38,500,000
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Granted In Period Weighted Average Remaining Contractual Term	2 years 73 days					6 years 40 days
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period						4 years				4 years	4 years
Share Based Compensation Arrangement By Share Based Payment Award Expiry Period From Date Of Grant						7 years
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition						4 years				4 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number (in Shares)						2,000,000	[1],[2]	2,500,000				2,500,000	[3],[4]	3,100,000		100,545	97,268							1,200,000
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Outstanding Intrinsic Value	42,900,000
Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested And Expected To Vest Exercisable Aggregate Intrinsic Value	23,100,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in Shares)	300,000					400,000						700,000	[5]		700,000	11,373				300,000			400,000
Share Based Compensation Arrangement By Share Based Payment Award Percentage Of Shares Authorized For Grant																					0.00%	200.00%
Share Based Compensation Arrangement by Share Based Payment Award Percentage of Shares Achieved	104.30%
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Outstanding, Weighted Average Remaining Contractual Terms	328 days
Base Fee Percentage																50.00%
Proceeds from Stock Options Exercised			20,700,000															8,600,000	16,600,000
Share Based Compensation Arrangement By Employee Stock Purchase Plan Stock Purchases As Percentage Of Employee Compensation Maximum																									10.00%
Share Based Compensation Arrangement By Share Based Payment Award Maximum Share Value Authorized For Purchase Under Employee Stock Purchase Plan																									23,750
Share Based Compensation Arrangemen tBy Share Based Paymen tAward Exercisable Price Percentage Of Closing Price Of Another Class Of Stock																									95.00%
Employee Stock Purchase Plan Maximum Number Of Shares That May Be Purchased By Eligible Participants (in Shares)																									1,300,000
Proceeds from Stock Plans			$ 2,800,000																						$ 3,800,000	$ 3,400,000

[1] At December 31, 2012, 1.2 million of these SARs were unvested. The Company expects that substantially all of these unvested awards will vest in future periods.

[2] At December 31, 2012, SARs outstanding had an intrinsic value of $42.9 million. SARs vested and exercisable had an intrinsic value of $23.1 million.

[3] The Company expects that substantially all of the outstanding awards at December 31, 2012 will vest in future periods.

[4] The weighted-average remaining contractual term of the outstanding RSUs is approximately 0.9 years.

[5] The 0.7 million RSUs granted in 2012 consisted of 0.3 million performance-based RSUs awarded to executives and 0.4 million service-based RSUs awarded to non-executive employees and certain board members. The 0.3 million performance-based RSUs awarded to executive personnel represented the target amount of the RSU award for the year, which was tied to an increase in the Company's subscription-based Research contract value ("CV") for 2012. The final number of performance-based RSUs granted could range from 0% to 200% of the target amount, with the final amount dependent on the actual increase in CV for the year as measured on December 31, 2012. The actual CV increase achieved for 2012 was 104.3% of the targeted amount, which resulted in the grant of 0.3 million performance-based RSUs to executives.