Stock-Based Compensation - Summary of Stock-Based Compensation Grants (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014
Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Awards Granted	3,623
Weighted-Average Grant Price Per Share	$ 38.17
Time-Based Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Awards Granted	66,409
Weighted-Average Grant Price Per Share	$ 32.69
Performance-Based Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Awards Granted	42,676
Weighted-Average Grant Price Per Share	$ 33.72