Stock-Based Compensation - Summary of Stock-Based Compensation Grants (Detail)	6 Months Ended
Jun. 30, 2019 $ / shares shares
Time Based Restricted Stock Units [Member]
Stock Awards Granted \| shares	26,325
Weighted-Average Grant Price Per Share \| $ / shares	$ 77.53
Performance Based Restricted Stock Units [Member]
Stock Awards Granted \| shares	80,104
Weighted-Average Grant Price Per Share \| $ / shares	$ 47.89
Stock Appreciation Rights [Member]
Stock Awards Granted \| shares	24,536
Weighted-Average Grant Price Per Share \| $ / shares	$ 77.70

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration