Stock-Based Compensation (Detail) - Stock-Based Compensation Expense By Award Type (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Total expense (1)	$ 9,200,000	[1]	$ 7,800,000	[1]	$ 28,021,000	[1]	$ 24,750,000	[1]
Stock Appreciation Rights (SARs) [Member]
Stock-based compensation expense	2,400,000		1,000,000		5,000,000		3,400,000
Common Stock Equivalents (CSEs) [Member]
Stock-based compensation expense	100,000		100,000		400,000		400,000
Restricted Stock Units (RSUs) [Member]
Stock-based compensation expense	$ 6,700,000		$ 6,700,000		$ 22,600,000		$ 21,000,000

[1] The three months ended September 30, 2012 and 2011 included charges of $1.5 million and $0.2 million, respectively, related to awards to retirement-eligible employees, since awards granted to retirement-eligible employees vest on an accelerated basis. The nine months ended September 30, 2012 and 2011 included charges of $4.7 million and $3.0 million, respectively, for retirement-eligible employees.