Stock Based Compensation - Summary of Stock Option and Stock Appreciation Rights ("SARs") Activity (Detail)	9 Months Ended
	Sep. 30, 2019 shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Outstanding Opening	39,800,000
Granted	300,000
Cancelled/forfeited	(1,200,000)
Exercised	(3,000,000.0)
Number of Shares, Outstanding Closing	35,900,000