Stock-Based Compensation Expense By Award Type (Detail) (USD $)	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 7,900,000	[1]	$ 7,800,000	[1]	$ 18,802,000	[1]	$ 16,993,000	[1]
Stock Appreciation Rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	1,000,000		900,000		2,600,000		2,400,000
Common Stock Equivalents
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	200,000		100,000		300,000		300,000
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 6,700,000		$ 6,800,000		$ 15,900,000		$ 14,300,000

[1] The three months ended June 30, 2012 and 2011 includes charges of $0.2 million and $0.3 million, respectively, related to awards to retirement-eligible employees, since a portion of the awards granted to retirement-eligible employees vest immediately. The six months ended June 30, 2012 and 2011 includes charges of $3.2 million and $2.8 million, respectively, for retirement-eligible employees.