Shareholders' Equity (Details) - USD ($) $ / shares in Units, shares in Millions		1 Months Ended		3 Months Ended	12 Months Ended
	Jan. 28, 2020	Nov. 30, 2019	Sep. 30, 2019	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Cumulative effect to reclassify certain tax effects from accumulated other comprehensive loss							$ (10,422,000)
Shares repurchased during period (in shares)					8.7	16.0
Shares repurchased, weighted average price per share (in dollars per share)					$ 13.13	$ 10.95
Remaining authorized repurchase amount					$ 111,000,000	$ 25,000,000
Common stock, dividends, per share, cash paid (in dollars per share)		$ 0.06	$ 0.06
Payments of ordinary dividends, common stock					$ 41,914,000	$ 0	$ 0
2% Convertible Senior Notes due 2020
Debt Instrument [Line Items]
Stated interest rate (in hundredths)				2.00%			2.00%
Principal amount of notes converted into shares				$ 202,500,000			$ 202,500,000
Shares issued during period upon conversion of convertible debt (in shares)							29.1
Treasury stock reissued during period upon conversion of notes (in shares)							18.7
Stock issued during period upon conversion of notes, new issues (in shares)							10.4
Accumulated other comprehensive loss
Debt Instrument [Line Items]
Cumulative effect to reclassify certain tax effects from accumulated other comprehensive loss				(10,400,000)			$ (10,422,000)
Retained earnings
Debt Instrument [Line Items]
Cumulative effect to reclassify certain tax effects from accumulated other comprehensive loss				$ 10,400,000			$ 10,422,000
Subsequent Event
Debt Instrument [Line Items]
Stock repurchase program, authorized amount	$ 300,000,000
Common stock, dividends, per share, declared (in dollars per share)	$ 0.06