Lease Commitments - Operating Leases Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Cash paid for amounts included in the measurement of operating lease liabilities	$ 108	$ 106
Right-of-use assets obtained in exchange for new operating lease liabilities	$ 36	$ 41
Weighted-average remaining lease term (years)	6 years	6 years 9 months 18 days
Weighted-average discount rate applied to operating leases (percent)	3.60%	3.60%