Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of contingently issuable shares. Contingently issuable shares are those shares that are issuable for little or no cash contingent on certain conditions being met.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 55
-URI http://asc.fasb.org/extlink&oid=117326831&loc=d3e2626-109256

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 48
-URI http://asc.fasb.org/extlink&oid=117326831&loc=d3e2538-109256

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

Earnings Per Common Share - Additional Information (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Schedule Of Antidilutive Securities Included In Computation Of Earnings Per Share [Line Items]
Shares contingently issuable under shareholder return plan			40,608	42,912
Stock Option [Member]
Schedule Of Antidilutive Securities Included In Computation Of Earnings Per Share [Line Items]
Securities excluded from computation of net income per diluted shares	353,829	117,600	117,600	117,600
Restricted Stock [Member]
Schedule Of Antidilutive Securities Included In Computation Of Earnings Per Share [Line Items]
Shares contingently issuable under shareholder return plan			30,137	17,081