Stock Compensation Plans - Stock-Based Compensation Expense and Related Tax Benefits (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 5,940	$ 5,974
Less: tax benefit	(1,726)	(1,907)
Total stock-based compensation expense, after tax	4,214	4,067
Equity-based awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	4,695	4,523
Liability-based awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 1,245	$ 1,451