Retirement Plans - Schedule of Accumulated Benefit Obligation, Change in Benefit Obligation, Change in Plan Assets, Plans' Funded Status and Amount Included in Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Benefit Obligation
Accumulated benefit obligation	$ 172	$ 187
Projected benefit obligation at beginning of year	187	175
Interest cost	4	6	$ 7
Actuarial loss (gain)	(8)	17
Benefits paid	(11)	(11)
Projected benefit obligation at end of year	172	187	175
Fair Value of Plan Assets
Fair value of plan assets at beginning of year	189	173
Actual return on plan assets	22	20
Corporation contribution	1	7
Benefits paid	(11)	(11)
Fair value of plan assets at end of year	201	189	173
Funded status of plans	29	2
Qualified Pension Plans
Benefit Obligation
Accumulated benefit obligation	154	167
Projected benefit obligation at beginning of year	167	156
Interest cost	4	5
Actuarial loss (gain)	(7)	15
Benefits paid	(10)	(9)
Projected benefit obligation at end of year	154	167	156
Fair Value of Plan Assets
Fair value of plan assets at beginning of year	189	173
Actual return on plan assets	22	20
Corporation contribution	0	5
Benefits paid	(10)	(9)
Fair value of plan assets at end of year	201	189	173
Funded status of plans	47	22
Non Qualified Pension Plans
Benefit Obligation
Accumulated benefit obligation	18	20
Projected benefit obligation at beginning of year	20	19
Interest cost	0	1
Actuarial loss (gain)	(1)	2
Benefits paid	(1)	(2)
Projected benefit obligation at end of year	18	20	19
Fair Value of Plan Assets
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Corporation contribution	1	2
Benefits paid	(1)	(2)
Fair value of plan assets at end of year	0	0	$ 0
Funded status of plans	$ (18)	$ (20)