Stock-Based Compensation - Short-term Incentive Plan - Additional Information (Detail) - Short-Term Incentive Plan (STIP) [Member]	3 Months Ended
	Mar. 31, 2018
Certain Executives [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of incentive awards in shares	50.00%
Percentage of incentive awards in cash	50.00%
All Other Participants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of incentive awards in cash	100.00%