Stock Compensation Plans - Stock-Based Compensation Expense and Related Tax Benefits (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 5,864	$ 4,870	$ 21,996	$ 17,713
Less: tax benefit	(1,735)	(1,511)	(6,756)	(5,546)
Total stock-based compensation expense, after tax	4,129	3,359	15,240	12,167
Equity-based awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	4,869	4,091	18,919	15,363
Liability-based awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 995	$ 779	$ 3,077	$ 2,350