Pension and Postretirement Benefit Plans - Additional Information (Details) - Pension Plan [Member] - UNITED STATES $ in Millions	Dec. 31, 2018 USD ($) plan
Defined Benefit Plan Disclosure [Line Items]
Number Of Plans Terminated | plan	1
Terminated Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Benefit Obligation	$ 938
Defined Benefit Plan, Plan Assets, Amount	773
Defined Benefit Plan, AOCI Losses	$ 370