Stock-Based Compensation - Summary of Stock-Based Compensation Grants (Detail) - $ / shares	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Time Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Awards Granted	19,516
Weighted-Average Grant Price Per Share	$ 70.05
Performance Based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Awards Granted	40,216
Weighted-Average Grant Price Per Share	$ 56.19
Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Awards Granted	16,340	0
Weighted-Average Grant Price Per Share	$ 70.09