Shareholder's Equity (Detail) - USD ($)		12 Months Ended
	May 08, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 08, 2020
Shareholders Equity
Common stock, shares authorized		426,000,000.0	426,000,000.0
Common stock, par value (per share)		$ 0.01	$ 0.01
Stock Repurchased During Period, Value		$ 150,200,000	$ 150,000,000.0	$ 500,000,000.0
Increase (Decrease) to Quarterly Dividend Rate					5.00%
Prior Quarter Approved Quarterly Dividend			19.00%
Dividends payable amount per share		$ 0.20
Dividends payable		$ 33,200,000	$ 32,000,000.0
Dividends paid per common share		$ 0.76	$ 0.72	$ 1.05
May 2018 Share Repurchase Program [Member]
Shareholders Equity
Authorized amount to repurchase shares of common stock	$ 750,000,000.0
Stock Repurchase Program Expiration Date	May 31, 2021
Common stock shares repurchased, shares		150,200,000
Stock Repurchased During Period, Value			$ 150,000,000.0
Remaining authorized repurchase amount		$ 99,700,000
Stock Repurchased During Period, Shares		3,700,000	4,000,000.0
December 2020 Share Repurchase Program [Member]
Shareholders Equity
Authorized amount to repurchase shares of common stock					$ 750,000,000.0
Remaining authorized repurchase amount		$ 750,000,000.0