Stock-Based Compensation - Summary of Nonvested Restricted Stock Unit Activity and Related Information (Detail) shares in Millions	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Nonvested Shares
Beginning Balance | shares	5.4
Granted | shares	3.8
Forfeited | shares	(0.1)
Vested | shares	(3.2)
Ending balance | shares	5.9
Weighted-Average Fair Value
Beginning Balance | $ / shares	$ 15.01	[1]
Granted | $ / shares	13.16	[1]
Forfeited | $ / shares	13.12	[1]
Vested | $ / shares	13.92	[1]
Ending Balance | $ / shares	$ 14.78	[1]

[1] Performance-based shares are valued utilizing a Monte Carlo valuation method using measures of total shareholder return. All other shares are valued at the grant-date market price.