Earnings Per Share - Computations of Basic and Diluted Earnings Per Share (Parenthetical) (Detail) - shares	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2017
Options and Stock Appreciation Rights (SARs) [Member]
Earnings Per Share Basic [Line Items]
Options to purchase shares of common stock were excluded from the computations of diluted earnings per share	194,949	98,878	37,261

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

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