Pension Plans - Additional Information (Detail) - USD ($)	6 Months Ended	12 Months Ended
Jun. 30, 2017	Dec. 31, 2016
Compensation And Retirement Disclosure [Abstract]
Fair value of pension plan assets	$ 14,963,000	$ 15,038,000
Employer contributions to 401(k) plan	$ 0	$ 339,000
Maximum employer matching contribution percentage	4.00%

Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

Name:	us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant