Share-Based Compensation - Schedule of Stock Options Outstanding and Exercisable (Detail)	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Outstanding, Shares | shares	935,000
Options Exercisable, Shares | shares	679,000
$26.68-$33.95
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price Range, minimum (in dollars per share)	$ 26.68
Exercise Price Range, maximum (in dollars per share)	$ 33.95
Options Outstanding, Shares | shares	200,000
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 31.39
Options Outstanding, Weighted Average Remaining Contractual Term (in Years)	4 years 8 months 12 days
Options Exercisable, Shares | shares	124,000
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 31.38
$34.33-$36.04
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price Range, minimum (in dollars per share)	34.33
Exercise Price Range, maximum (in dollars per share)	$ 36.04
Options Outstanding, Shares | shares	193,000
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 34.74
Options Outstanding, Weighted Average Remaining Contractual Term (in Years)	5 years 4 months 25 days
Options Exercisable, Shares | shares	152,000
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 34.85
$36.43-$36.89
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price Range, minimum (in dollars per share)	36.43
Exercise Price Range, maximum (in dollars per share)	$ 39.89
Options Outstanding, Shares | shares	222,000
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 36.79
Options Outstanding, Weighted Average Remaining Contractual Term (in Years)	5 years 8 months 12 days
Options Exercisable, Shares | shares	179,000
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 36.81
$37.09-$40.36
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price Range, minimum (in dollars per share)	37.09
Exercise Price Range, maximum (in dollars per share)	$ 40.36
Options Outstanding, Shares | shares	245,000
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 39.27
Options Outstanding, Weighted Average Remaining Contractual Term (in Years)	5 years 3 months 18 days
Options Exercisable, Shares | shares	158,000
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 38.67
$41.69-$55.99
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price Range, minimum (in dollars per share)	41.69
Exercise Price Range, maximum (in dollars per share)	$ 55.99
Options Outstanding, Shares | shares	75,000
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 44.62
Options Outstanding, Weighted Average Remaining Contractual Term (in Years)	1 year 4 months 25 days
Options Exercisable, Shares | shares	66,000
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 44.88