Stock-Based Compensation (Detail) - Stock-Based Compensation Expense By Award Type (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 7,200	[1]	$ 0	[1]	$ 19,574	[1]	$ 18,802	[1]
Stock appreciation rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	1,200		0		3,000		2,600
Common stock equivalents (CSEs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	100		0		300		300
Restricted stock units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 5,900		$ 0		$ 16,300		$ 15,900

[1] Includes charges of $1.7 million and $0.2 million for the three months ended June 30, 2013 and 2012, respectively, for awards to retirement-eligible employees since these awards vest on an accelerated basis. The six months ended June 30, 2013 and 2012 include retirement-eligible charges of $8.8 million and $3.2 million, respectively.