Defined Benefit Plans - Assumed Health Care Cost Trend Rates Used to Determine Benefit Obligations and Net Cost (Detail) - Postretirement Benefits [Member]		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Rate that the cost trend rate is assumed to decline (the ultimate trend rate)		4.50%	4.50%
Year that the rate reaches the ultimate trend rate		2028	2027
Pre Age Sixty Five
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed for next year	[1]	6.30%	6.40%
Post Age Sixty Five
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate assumed for next year	[1]	6.70%	7.40%

[1] The pre-65 initial health care cost trend rate is shown first / followed by the post-65 rate