Stock-Based Compensation (Detail) - Stock-Based Compensation Expense By Award Type (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 16,700	[1]	$ 13,800	[1]
Retirement eligible employees equity award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	10,500		7,700
Stock appreciation rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	2,100		1,900
Common stock equivalents (CSEs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	200		200
Restricted stock units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 14,400		$ 11,700

[1] Includes charges of $10.5 million and $7.7 million for the three months ended March 31, 2015 and 2014, respectively, for awards to retirement-eligible employees since these awards vest on an accelerated basis.