Stock-Based Compensation (Detail) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012		Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant	6,100,000				6,100,000
Common stock par value	$ 0.0005				$ 0.0005				$ 0.0005
Stock-based compensation expense	$ 7,400,000	[1]	$ 0	[1]	$ 27,049,000	[1]	$ 28,021,000	[1]
Total share-based compensation cost not yet recognized	48,400,000				48,400,000
Total share-based compensation cost not yet recognized, remaining weighted average service period					2 years 3 months 18 days
Retirement eligible employees equity award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	1,800,000		1,500,000		10,600,000		4,700,000
Stock appreciation rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	1,100,000		0		4,100,000		5,000,000
Total share-based compensation cost not yet recognized, remaining weighted average service period					6 years 4 months 13 days
Award vesting period					4 years
Award expiry period from date of grant					7 years
Total compensation cost not yet recognized, period for recognition					4 years
Outstanding shares unvested	2,000,000	[2],[3]			2,000,000	[2],[3]			2,000,000
Aggregate Intrinsic value of outstanding shares	59,300,000				59,300,000
Aggregate intrinsic value of shares vested and exercisable	39,800,000				39,800,000
Stock grants during period					400,000
Restricted stock units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	6,200,000		0		22,500,000		22,600,000
Outstanding shares unvested	1,800,000	[4],[5]			1,800,000	[4],[5]			2,500,000
Stock grants during period					600,000	[6]
Weighted average remaining contractual terms					1 year 2 months 12 days
Restricted stock units (RSUs) | Executive officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock grants during period					300,000
Restricted stock units (RSUs) | Non executive
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock grants during period					300,000
Common stock equivalents (CSEs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding shares unvested	102,019.000				102,019.000				100,545
Stock grants during period					7,449
Base fee percentage					50.00%
Target amount | Restricted stock units (RSUs) | Executive officer | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares authorized for grant					0.00%
Target amount | Restricted stock units (RSUs) | Executive officer | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares authorized for grant					200.00%
Unvested | Stock appreciation rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding shares unvested	1,000,000				1,000,000
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee stock purchase plan, stock purchases as percentage of employee compensation maximum	10.00%				10.00%
Maximum share value authorized for purchase under employee stock purchase plan					23,750
Exercisable price percentage of closing price of another class of stock	95.00%				95.00%
Maximum number of shares that may be purchased by eligible participants	1,200,000				1,200,000
Proceeds from stock plans					$ 3,300,000		$ 2,900,000

[1] Includes charges of $1.8 million and $1.5 million for the three months ended September 30, 2013 and 2012, respectively, for awards to retirement-eligible employees since these awards vest on an accelerated basis. The nine months ended September 30, 2013 and 2012 include retirement-eligible charges of $10.6 million and $4.7 million, respectively.

[2] Total SARs outstanding had an intrinsic value of $59.3 million. SARs vested and exercisable had an intrinsic value of $39.8 million.

[3] As of September 30, 2013, 1.0 million of the SARs outstanding were unvested. The Company expects that substantially all of these unvested awards will vest in future periods.

[4] The weighted-average remaining contractual term of the outstanding RSUs is approximately 1.2 years.

[5] The Company expects that substantially all of the outstanding awards will vest in future periods.

[6] The 0.6 million RSUs granted in 2013 consisted of 0.3 million performance-based RSUs awarded to executives and 0.3 million service-based RSUs awarded to non-executive employees and certain board members. The 0.3 million performance-based RSUs represents the target amount of the award for the year, which is tied to an increase in the Company’s subscription-based Research contract value (“CV”) for 2013. The final number of performance-based RSUs that will be granted to executives in 2013 ranges from 0% to 200% of the target amount, with the final number dependent on the actual increase in CV for the year as measured on December 31, 2013. If the specified minimum level of achievement is not met, the performance-based RSUs will be forfeited in their entirety, and any compensation expense previously recorded will be reversed.