Shareholders' Equity - Accumulated Other Comprehensive Loss (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ 24,400,000	$ 240,800,000
Other comprehensive (loss) income before reclassifications, net of tax (1)	(3,500,000)
Amounts reclassified from accumulated other comprehensive loss, net of tax	79,000,000
Net current period other comprehensive income (loss)	75,500,000	(11,300,000)
Ending balance	(25,300,000)	24,400,000
Liability adjustments for defined benefit plans	0
Accumulated foreign currency translation losses	1,000,000
Gains (Losses) on Derivative Financial Instruments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	0
Other comprehensive (loss) income before reclassifications, net of tax (1)
Amounts reclassified from accumulated other comprehensive loss, net of tax
Net current period other comprehensive income (loss)	0
Ending balance	0	0
Defined Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(20,100,000)
Other comprehensive (loss) income before reclassifications, net of tax (1)	(2,700,000)
Amounts reclassified from accumulated other comprehensive loss, net of tax	3,200,000
Net current period other comprehensive income (loss)	500,000
Ending balance	(19,600,000)	(20,100,000)
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(76,000,000)
Other comprehensive (loss) income before reclassifications, net of tax (1)	(800,000)
Amounts reclassified from accumulated other comprehensive loss, net of tax	75,800,000
Net current period other comprehensive income (loss)	75,000,000
Ending balance	(1,000,000)	(76,000,000)
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(96,100,000)	(84,800,000)
Ending balance	$ (20,600,000)	$ (96,100,000)