Subsequent Events (Narrative) (Detail) - USD ($)	2 Months Ended	3 Months Ended		9 Months Ended	12 Months Ended
	Mar. 10, 2020	Mar. 10, 2020	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 16, 2019	Dec. 09, 2019	Sep. 24, 2018	Sep. 25, 2017	Mar. 02, 2017
Subsequent Event [Line Items]
Stock Repurchased During Period, Shares			31,000,000	8,700,000	26,321,293	16,660,566	13,346,389
Treasury Stock Acquired, Average Cost Per Share			$ 3.22	$ 3		$ 2.25
Stock Repurchased During Period, Value			$ 100,000,000	$ 25,000,000		$ 30,000,000
Extinguishment of Debt, Amount					$ 0	$ 0	$ 43,909,000
Stock Repurchase Program, Authorized Amount					275,000,000			$ 75,000,000	$ 200,000,000	$ 100,000,000	$ 25,000,000	$ 30,000,000
December 2021 Notes [Member]
Subsequent Event [Line Items]
Extinguishment of Debt, Amount					44,800,000
December 2024 Notes [Member]
Subsequent Event [Line Items]
Extinguishment of Debt, Amount					$ 74,600,000
Subsequent Event [Member]
Subsequent Event [Line Items]
Stock Repurchased During Period, Shares	3,800,000	7,000,000
Treasury Stock Acquired, Average Cost Per Share	$ 3.42	$ 3.43
Stock Repurchased During Period, Value	$ 12,900,000	$ 23,900,000
Extinguishment of Debt, Amount		$ 133,000,000
Share-based Compensation Arrangement by Share-based Payment Award Accelerated Compensation Cost	16,300,000.000000000
Subsequent Event [Member] | December 2021 Notes [Member]
Subsequent Event [Line Items]
Extinguishment of Debt, Amount	3,200,000
Subsequent Event [Member] | December 2024 Notes [Member]
Subsequent Event [Line Items]
Extinguishment of Debt, Amount	$ 10,500,000