Stock Compensation Plans - Stock-Based Compensation Expense Included in Consolidated Statement of Income and Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	$ 23,010	$ 23,591	$ 22,001
Less tax benefit	(7,228)	(7,730)	(8,028)
Total stock-based compensation, net of tax	15,782	15,861	13,973
Equity-based awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	19,716	20,547	18,382
Liability-based awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	$ 3,294	$ 3,044	$ 3,619