Statement of Consolidated Cash Flows - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income (loss)		$ 91.7	$ (236.6)	$ 71.8
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation of property, plant and equipment		34.5	30.8	29.5
Amortization of definite-lived intangible assets		1.5	1.6	1.6
Amortization of debt discount and debt issuance costs		1.1	4.3	11.8
Deferred income taxes1	[1]	57.4	(131.7)	34.3
Excess tax benefit upon vesting of non-vested shares and dividend payment on unvested shares expected to vest2	[2]	0.0	(1.3)	(0.8)
Non-cash equity compensation2	[2]	11.8	9.5	7.0
Lower of cost or market inventory write-down		4.9	2.6	0.0
Non-cash unrealized (gain) loss on derivative instruments		(18.7)	3.4	6.8
Non-cash impairment charges		2.8	0.1	1.5
Loss on repurchase of Senior Notes	[3]	11.1	2.5	0.0
Loss on disposition of property, plant and equipment		0.2	0.3	0.2
Loss on disposition of available for sale securities		0.0	0.0	0.1
Non-cash defined benefit net periodic benefit cost (income)	[4]	3.7	2.8	(23.5)
Non-cash loss on removal of Union VEBA, net	[4]	0.0	(446.7)	0.0
Other non-cash changes in assets and liabilities		(1.2)	(0.6)	(0.6)
Changes in operating assets and liabilities:
Trade and other receivables		(26.8)	17.4	(7.0)
Inventories, excluding lower of cost or market write-down5	[5]	13.1	(7.5)	(0.3)
Prepaid expenses and other current assets	[5],[6]	(8.0)	0.5	(0.6)
Accounts payable		3.4	(13.6)	20.3
Accrued liabilities	[4],[6]	26.2	12.8	(6.0)
Annual variable cash contributions to VEBAs	[4]	(19.5)	(13.7)	(16.0)
Long-term assets and liabilities, net	[4],[5],[6]	(27.3)	27.3	(7.2)
Net cash provided by operating activities		164.3	158.8	124.1
Cash flows from investing activities:
Capital expenditures		(76.1)	(63.1)	(59.4)
Purchase of available for sale securities		(255.3)	(0.5)	(93.5)
Proceeds from disposition of available for sale securities		55.0	84.0	108.2
Net cash (used in) provided by investing activities	[7]	(276.4)	20.4	(44.7)
Cash flows from financing activities:
Repayment of principal and redemption premium of 8.25% Senior Notes	[3]	(206.0)	(30.0)	0.0
Issuance of 5.875% Senior Notes		375.0	0.0	0.0
Repayment of Convertible Notes	[5]	0.0	(175.0)	0.0
Proceeds from cash-settled call options related to settlement of Convertible Notes	[5]	0.0	94.9	0.0
Payment for conversion premium related to settlement of Convertible Notes	[3]	0.0	(94.9)	0.0
Cash paid for debt issuance costs		6.8	0.6	0.0
Proceeds from stock option exercises		1.2	0.0	0.0
Repayment of capital lease		0.0	0.0	(0.1)
Excess tax benefit upon vesting of non-vested shares and dividend payment on unvested shares expected to vest		0.0	1.3	0.8
Cancellation of shares to cover employees' tax withholdings upon vesting of non-vested shares		(2.9)	(2.8)	(2.4)
Repurchase of common stock		(33.3)	(49.2)	(44.1)
Cash dividends paid to stockholders		(32.4)	(28.1)	(25.4)
Net cash provided by (used in) financing activities	[7]	94.8	(284.4)	(71.2)
Net (decrease) increase in cash and cash equivalents during the period		(17.3)	(105.2)	8.2
Cash and cash equivalents at beginning of period		72.5	177.7	169.5
Cash and cash equivalents at end of period		$ 55.2	$ 72.5	$ 177.7

[1] See Note 1 for discussion of our adoption of ASU 2015-17.

[2] See Note 5 and Note 8 for discussion of our adoption of ASU 2016-09 (as defined in Note 1).

[3] See Note 3 for more information relating to the 8.25% Senior Notes (defined in Note 3) and the Convertible Notes.

[4] See Note 6 for the impact of removing the Union VEBA (defined in Note 6) net assets.

[5] See Note 2 for the impact of reclassifying repair parts to other current and other long-term assets.

[6] Excludes the reclassification of derivatives relating to the Convertible Notes (defined in Note 3) from long-term to current at December 31, 2014 as the amounts had no impact on cash flow - see Note 3 and Note 10.

[7] See Note 13 for supplemental disclosure on non-cash transactions.