Stock-Based Compensation Plans - Stock-Based Compensation Expense (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	$ 2,241	$ 2,156	$ 6,419	$ 6,184
Employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	2,058	1,968	5,978	5,748
Employee [Member] | Restricted Stock and Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	1,820	1,796	5,317	5,270
Employee [Member] | Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	238	172	661	478
Non-Employee Directors [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	$ 183	$ 188	$ 441	$ 436