Statement of Consolidated Cash Flows $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)		Dec. 31, 2016 USD ($)		Dec. 31, 2015 USD ($)
Cash flows from operating activities:
Net income (loss)	$ 45.4		$ 91.7		$ (236.6)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation of property, plant and equipment	38.3		34.5		30.8
Amortization of definite-lived intangible assets	1.4		1.5		1.6
Amortization of debt discount and debt issuance costs	1.2		1.1		4.3
Deferred income taxes	89.0		57.4		(131.7)
Excess tax benefit upon vesting of non-vested shares and dividend payment on unvested shares expected to vest	0.0		0.0		(1.3)
Non-cash compensation	13.3		11.8		9.5
Lower of cost or market inventory write-down	0.0		4.9		2.6
Non-cash unrealized (gain) loss on derivative instruments	(19.4)		(18.7)		3.4
Non-cash impairment charges	19.2		2.8		0.1
Loss on repurchase of Senior Notes	0.0		11.1		2.5
(Gain) loss on disposition of property, plant and equipment	(0.5)		0.2		0.3
Gain on disposition of available for sale securities	(2.3)		0.0		0.0
Non-cash defined benefit net periodic benefit cost (income)	4.8		3.7		2.8
Non-cash loss on removal of Union VEBA, net	0.0		0.0		(446.7)
Other non-cash changes in assets and liabilities	(3.9)		(1.2)		(0.6)
Changes in operating assets and liabilities:
Trade and other receivables	(30.9)		(26.8)		17.4
Inventories, excluding lower of cost or market write-down	(6.3)		13.1		(7.5)
Prepaid expenses and other current assets	(1.7)		(8.0)		0.5
Accounts payable	13.0		3.4		(13.6)
Accrued liabilities	(4.7)		26.2		12.8
Annual variable cash contributions to VEBAs	(20.0)		(19.5)		(13.7)
Long-term assets and liabilities, net	(2.2)		(26.0)		28.2
Net cash provided by operating activities	141.5		165.6		159.7
Cash flows from investing activities:
Capital expenditures	(75.5)		(76.1)		(63.1)
Purchase of available for sale securities	(247.5)		(255.3)		(0.5)
Proceeds from disposition of available for sale securities	296.9		55.0		84.0
Proceeds from disposal of property, plant and equipment	0.6		0.0		0.0
Net cash (used in) provided by investing activities	(25.5)	[1]	(276.4)	[1]	20.4	[1]
Cash flows from financing activities:
Repayment of principal and redemption premium of 8.25% Senior Notes	0.0		(206.0)		(30.0)
Issuance of 5.875% Senior Notes	0.0		375.0		0.0
Repayment of Convertible Notes	0.0		0.0		(175.0)
Proceeds from cash-settled call options related to settlement of Convertible Notes	0.0		0.0		94.9
Payment for conversion premium related to settlement of Convertible Notes	0.0		0.0		(94.9)
Cash paid for debt issuance costs	0.0		6.8		0.6
Proceeds from stock option exercises	0.0		1.2		0.0
Repayment of capital lease	(0.4)		0.0		0.0
Excess tax benefit upon vesting of non-vested shares and dividend payment on unvested shares expected to vest	0.0		0.0		1.3
Cancellation of shares to cover employees' tax withholdings upon vesting of non-vested shares	(4.5)		(2.9)		(2.8)
Repurchase of common stock	(79.5)		(33.3)		(49.2)
Cash dividends and dividend equivalents paid	(35.0)		(32.4)		(28.1)
Net cash (used in) provided by financing activities	(119.4)	[1]	94.8	[1]	(284.4)	[1]
Net decrease in cash, cash equivalents and restricted cash during the period	(3.4)		(16.0)		(104.3)
Cash, cash equivalents and restricted cash at end of period	51.1		55.2		72.5
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 64.3		$ 67.7		$ 83.7

[1] See Note 14 for supplemental disclosure on non-cash transactions.