Share-based Compensation - Summary of SARs Activity (Detail)	9 Months Ended
	Sep. 30, 2019 $ / shares shares
Stock-Settled SARs Activity [Member]
Shares
Outstanding, beginning balance (in shares) | shares	810,759
Exercised (in shares) | shares	(148,729)
Expired or forfeited (in shares) | shares	(7,167)
Outstanding, ending balance (in shares) | shares	654,863
Weighted-Average Exercise Price
Outstanding, beginning balance (in dollars per share) | $ / shares	$ 33.88
Exercised (in dollars per share) | $ / shares	34.71
Expired or forfeited (in dollars per share) | $ / shares	37.85
Outstanding, ending balance (in dollars per share) | $ / shares	$ 33.68
Cash Settled S A Rs Activity [Member]
Shares
Outstanding, beginning balance (in shares) | shares	58,428
Exercised (in shares) | shares	(48,722)
Expired or forfeited (in shares) | shares	(1,193)
Outstanding, ending balance (in shares) | shares	8,513
Weighted-Average Exercise Price
Outstanding, beginning balance (in dollars per share) | $ / shares	$ 30.71
Exercised (in dollars per share) | $ / shares	30.34
Expired or forfeited (in dollars per share) | $ / shares	19.37
Outstanding, ending balance (in dollars per share) | $ / shares	$ 34.39