Earnings Per Share - Summary of Computations of Basic and Diluted Earnings Per Share Footnote (Detail) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Employee Stock Option | Common stock
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Share-based compensation awards purchased not included in calculation of diluted earnings per share (in shares)	4.5	3.1	4.5	3.0
Employee Stock Option | Restricted Stock
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Share-based compensation awards purchased not included in calculation of diluted earnings per share (in shares)	0.1	0.0	0.4	0.8
Warrants
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Share-based compensation awards purchased not included in calculation of diluted earnings per share (in shares)	7.6	7.6	7.6	6.0