Capital Stock - Additional Information (Details) - USD ($)		12 Months Ended
	Apr. 06, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	May 31, 2018
Equity Class Of Treasury Stock [Line Items]
Total cost of shares repurchased		$ 24,600,000	$ 143,000,000.0	$ 357,700,000
Dividends per share of common stock		$ 0.17	$ 0.64	$ 0.55
Dividends paid		$ 14,200,000	$ 54,200,000	$ 48,400,000
Dividend Declared
Equity Class Of Treasury Stock [Line Items]
Dividends payable, date declared	Apr. 06, 2020
Number of preferred share purchase right declared as divided per common stock	1
Dividends payable,record date	Apr. 06, 2020
Maximum percentage of common stock acquisition allowed by board of directors under rights plan	15.00%
Number of days after public announcement rights exercisable for acquiring person	10 days
Rights expiration date	Apr. 06, 2021
Dividend Declared | Series A Junior Participating Preferred Stock
Equity Class Of Treasury Stock [Line Items]
Exercise price of rights	$ 150.00
2018 Repurchase Plan
Equity Class Of Treasury Stock [Line Items]
Authorized amount to repurchase outstanding common stock					$ 500,000,000
Remaining authorized amount to repurchase outstanding common stock		$ 217,200,000