Statement of Consolidated Cash Flows - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net income		$ 36.0	$ 26.3
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property, plant and equipment		9.2	8.3
Amortization of definite-lived intangible assets		0.4	0.4
Amortization of debt discount and debt issuance costs		0.3	0.3
Deferred income taxes		18.1	15.1
Non-cash equity compensation		3.0	2.6
Lower of cost or market inventory write-down		0.0	4.9
Gain (Loss) on Sale of Investments		(0.7)	0.0
Non-cash unrealized gains on derivative instruments		(15.1)	(4.0)
Non-cash net periodic postretirement benefit cost relating to Salaried VEBA		1.1	0.8
Other non-cash changes in assets and liabilities		(1.2)	0.3
Changes in operating assets and liabilities:
Trade and other receivables		(19.2)	(24.6)
Inventories, excluding lower of cost or market write-down		(1.9)	4.1
Prepaid expenses and other current assets		(3.3)	(2.2)
Accounts payable		9.4	1.9
Accrued liabilities		(11.4)	21.2
Annual variable cash contributions to VEBAs		(20.0)	(19.5)
Long-term assets and liabilities, net		(0.6)	(14.6)
Net cash provided by operating activities		4.1	21.3
Cash flows from investing activities
Capital expenditures		(14.8)	(25.9)
Purchase of available for sale securities		(74.7)	0.0
Proceeds from disposition of available for sale securities		110.9	20.0
Net cash provided by (used in) investing activities	[1]	21.4	(5.9)
Cash flows from financing activities
Repayment of capital lease		(0.2)	0.0
Cancellation of shares to cover employees' tax withholdings upon vesting of non-vested shares		(4.4)	(2.7)
Repurchase of common stock		(32.6)	(6.3)
Payments of Dividends		9.3	8.2
Net cash used in financing activities	[1]	(46.5)	(17.2)
Net decrease in cash, cash equivalents and restricted cash during the period		(21.0)	(1.8)
Cash, cash equivalents and restricted cash at beginning of period		67.7	83.7
Cash, cash equivalents and restricted cash at end of period		$ 46.7	$ 81.9

[1] See Note 11 for the supplemental disclosure on non-cash transactions.