Income Taxes (Details) $ / shares in Units, $ in Millions, ₩ in Billions	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($) $ / shares	Sep. 30, 2016 USD ($) $ / shares	Sep. 30, 2017 USD ($) $ / shares	Sep. 30, 2017 KRW (₩)	Sep. 30, 2016 USD ($) $ / shares
United States	$ (28.2)	$ (13.0)	$ (46.7)		$ (38.6)
Foreign	72.8	61.4	162.2		178.6
Income before income taxes	44.6	48.4	115.6		140.1
Income tax provision	$ 82.6	$ 5.4	$ 92.2		$ 15.7
Effective income tax rate	185.00%	11.10%	79.80%	79.80%	11.20%
Effective income tax rate reconciliation, valuation allowance on U.S. deferred tax assets	$ 76.9		$ 76.9
Cumulative loss period	3 years
Income tax expense due to change in estimate related to uncertain tax positions	$ 1.7
Income tax expense due to change in estimate related to uncertain tax position and adjustment for ASU 2016-09			$ 5.6
Special income tax concession period			5 years	5 years
Decrease in foreign income taxes due to special income tax concession	$ 0.2	$ 0.6	$ 1.4		$ 2.3
Impact of income tax concession on basic earnings per common share (in dollars per share) | $ / shares	$ 0	$ 0.01	$ 0.02		$ 0.03
Impact of income tax concession on diluted earnings per common share (in dollars per share) | $ / shares	$ 0	$ 0.01	$ 0.02		$ 0.03
Tax Authority, South Korea (SRTO)
Income tax assessment notice, amount			$ 8.2	₩ 9.2
Without income tax benefit adjustment and valuation allowance
Effective income tax rate	12.50%		8.30%	8.30%
During 2017
Effective income tax rate reconciliation, valuation allowance on U.S. deferred tax assets	$ 24.0
Previous years
Effective income tax rate reconciliation, valuation allowance on U.S. deferred tax assets	$ 52.9