Defined Benefit Pension Plan and Postretirement Benefits - Additional Information (Detail)	6 Months Ended
Jun. 30, 2019
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Percentage of employer's contribution based on participants contribution	50.00%
Maximum [Member]
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
Percentage of employer's contribution based on participants compensation	2.00%

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

No definition available.

Name:	us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration