Share-Based Compensation - Schedule of Performance Based Awards Goals with Respect to TSR and ROIC (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
TSR Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Threshold Performance of Shares, percentage	50.00%	50.00%	50.00%
Target Performance of Shares, percentage	100.00%	100.00%	100.00%
Maximum Performance of Shares, percentage	150.00%	150.00%	150.00%
Threshold Performance, percentage	35.00%	35.00%	35.00%
Target Performance, percentage	50.00%	50.00%	50.00%
Maximum Performance, percentage	75.00%	75.00%	75.00%
ROIC Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Threshold Performance of Shares, percentage	35.00%	35.00%	35.00%
Target Performance of Shares, percentage	100.00%	100.00%	100.00%
Maximum Performance of Shares, percentage	150.00%	150.00%	150.00%
Threshold Performance, percentage	15.00%	15.50%	11.00%
Target Performance, percentage	17.50%	18.00%	12.50%
Maximum Performance, percentage	20.00%	20.50%	14.00%