Schedule of Defined Benefit Plans Disclosures (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure
Transfer out of Level 3		$ 2,700
Ending Balance	$ 168,500
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure
Interest and market value adjustments		59
Benefits paid		(40)
Other		(15)
Significant Unobservable Inputs (Level 3) | Group Annuity Insurance Contracts
Defined Benefit Plan Disclosure
Beginning Balance	$ 0	3,166
Transfer out of Level 3		(2,658)
Purchases of retiree annuity insurance contracts		(512)
Ending Balance		$ 0