Employee Stock Plans - Summary of Status of Senior Executive Plans (Detail) - $ / shares shares in Millions		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Shares
Granted		3.0	2.2	1.4
Vested		(1.1)	(1.2)	(0.9)
Restricted Stock | Executive Officer
Shares
Balance, at beginning of year		1.6	1.2	0.9
Granted	[1]	2.7	2.0	1.3
Vested	[2]	(0.9)	(1.1)	(0.7)
Forfeited/expired		(0.2)	(0.5)	(0.3)
Balance, at end of year		3.2	1.6	1.2
Issued in calendar year	[2]	0.6	0.4	0.4
Fair Value
Balance, at beginning of year		$ 10	$ 13	$ 14
Granted	[1]	14	10	14
Vested	[2]	17	15	19
Forfeited/expired		17	15	19
Balance, at end of year		12	10	13
Issued in calendar year	[2]	$ 15	$ 19	$ 17

[1] Shares granted in 2021 include one-third of two three-year performance awards. The performance goals for 2022 and 2023 were not set at the time of the agreement and, therefore, the portion of the awards related to those periods do not have a grant date fair value for accounting purposes and are not included in the chart above.

[2] Shares that vest at December 31 of each year are issued to the employees in the first quarter of the following year, although the requisite service period is complete. Accordingly, the 0.6 million shares issued in 2021 include shares vested at December 31, 2020, after adjusting for shares withheld to meet employee tax requirements. The shares withheld for employee tax requirements were valued at $7 million, $5.5 million and $5.4 million for 2021, 2020 and 2019, respectively.