Pension and Other Postretirement Benefits - Additional Information (Detail) $ in Millions	1 Months Ended
	Jul. 31, 2019 USD ($) Employee	Jun. 30, 2019 USD ($) Employee	Sep. 30, 2019 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Collective bargaining agreement term	6 years	6 years
Number of employees affected the change in defined benefit plans | Employee	900	700
Percentage of employers contribution in defined benefit plans	12.00%	12.00%
Additional contributions in defined benefit plans	$ 2	$ 2
Period to improve financial position of the target benefit plan	5 years	3 years
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Company contributions to the existing defined benefit plan in 2020			$ 5