Share-Based Compensation - Summary of Share-Based Compensation Expense (Detail) (USD $)	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]
Share-based compensation before income tax benefit	$ 1,202,000	$ 1,670,000	$ 3,569,000	$ 4,524,000
Income tax benefit	(445,000)	(571,000)	(1,326,000)	(1,606,000)
Total share-based compensation, net of income tax benefit	757,000	1,099,000	2,243,000	2,918,000
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation before income tax benefit	802,000	890,000	2,522,000	2,610,000
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation before income tax benefit	347,000	548,000	871,000	1,220,000
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation before income tax benefit	3,000	148,000	104,000	450,000
Restricted Stock Units and Performance Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation before income tax benefit	$ 50,000	$ 84,000	$ 72,000	$ 244,000