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, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 6,045	$ 5,864	$ 22,843	$ 21,996
Less: tax benefit	(1,899)	(1,735)	(6,970)	(6,756)
Total stock-based compensation expense, after tax	4,146	4,129	15,873	15,240
Equity-based awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	5,593	4,869	19,627	18,919
Liability-based awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 452	$ 995	$ 3,216	$ 3,077