Stock-Based Compensation Expense By Award Type (Detail) (USD $)	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 10,939,000	[1]	$ 9,162,000	[1]
Stock Appreciation Rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	1,600,000		1,500,000
Common Stock Equivalents
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	100,000		100,000
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 9,200,000		$ 7,600,000

[1] Includes charges of $3.0 million and $2.5 million for the three months ended March 31, 2012 and 2011 respectively, related to awards to retirement-eligible employees, since a portion of the awards vest immediately.