Stock-Based Compensation (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant	8,000,000
Stock-based compensation expense	$ 38,845,000		$ 34,735,000	$ 36,378,000
Total share-based compensation cost not yet recognized	44,900,000
Total share-based compensation expense not yet recognized, remaining weighted average service period	2 years 73 days
Aggregate intrinsic value of outstanding shares	58,500,000
Aggregate intrinsic value of shares vested and exercisable	30,800,000
Stock grants during period (in shares)	300,000
Award percentage of shares achieved	172.60%
Weighted average remaining contractual term	1 year
Target Amount | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent of shares authorized for grant	0.00%
Target Amount | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percent of shares authorized for grant	200.00%
Executive Officer | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock grants during period (in shares)	200,000
Executive Officer | Service-based Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock grants during period (in shares)	300,000
Unvested
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding shares unvested	800,000
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee stock purchase plan, stock purchases as a percentage of employee compensation, maximum	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%
Maximum number of shares that may be purchased by eligible participants	1,100,000
Proceeds from stock grants	7,800,000		6,000,000	12,400,000
Stock Appreciation Rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense not yet recognized, remaining weighted average service period	6 years 40 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	1,400,000	[1],[2]	1,600,000
Stock grants during period (in shares)	400,000
Stock Appreciation Rights (SARs) | Non Executive
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock grants during period (in shares)	300,000
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding shares unvested	1,400,000	[3],[4]	1,800,000
Stock grants during period (in shares)	600,000	[5]
Restricted Stock Units (RSUs) | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Stock grants during period (in shares)	600,000
Restricted Stock Units (RSUs) | Service-based Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Common Stock Equivalents (CSEs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding shares unvested	104,203		102,479
Stock grants during period (in shares)	8,509
Base fee percentage	50.00%
Retirement Eligible Employees Equity Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 14,800,000		$ 12,500,000	$ 5,100,000

[1] At December 31, 2014, 0.8 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, 2014, SARs outstanding had an intrinsic value of $58.5 million. SARs vested and exercisable had an intrinsic value of $30.8 million.

[3] The weighted-average remaining contractual term of the outstanding RSUs is approximately 1 year.

[4] The Company expects that substantially all of the outstanding awards at December 31, 2014 will vest in future periods.

[5] The 0.6 million RSUs granted in 2014 consisted of 0.3 million performance-based RSUs awarded to executives and 0.3 million service-based RSUs awarded to non-executive employees and non-management board members. The aggregate target number of performance-based RSUs awarded in 2014 was 0.2 million, subject to adjustment from 0% to 200% of the target number depending upon the increase in the Company's subscription-based contract value ("CV') measured on December 31, 2014 compared to December 31, 2013. The actual CV increase achieved for 2014 was 172.6%, which resulted in the final grant of approximately 0.3 million performance-based RSUs to the executives.