Statement of Consolidated Cash Flows (Unaudited) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net income		$ 29.1	$ 28.0
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property, plant and equipment		12.5	11.2
Amortization of definite-lived intangible assets		0.7	0.7
Amortization of debt discount and debt issuance costs		0.3	0.3
Deferred income taxes		14.8	10.4
Non-cash equity compensation		1.7	2.4
Gain on disposition of short-term investments		(0.5)	(0.3)
Loss on disposition of property, plant and equipment		0.2	0.0
Other non-cash changes in assets and liabilities		1.8	3.6
Changes in operating assets and liabilities:
Trade and other receivables		(12.6)	(12.8)
Contract assets		7.5	(3.5)
Inventories		(17.0)	(18.8)
Prepaid expenses and other current assets		(2.8)	(3.4)
Accounts payable		21.7	7.4
Accrued liabilities		(2.3)	(0.4)
Annual variable cash contributions to Salaried VEBA		(2.9)	(2.1)
Long-term assets and liabilities, net		0.2	0.1
Net cash provided by operating activities	[1]	52.4	22.8
Cash flows from investing activities
Capital expenditures		(21.1)	(13.6)
Purchase of short-term investments		(39.1)	(18.1)
Proceeds from disposition of short-term investments		78.8	32.7
Net cash provided by investing activities	[1]	18.6	1.0
Cash flows from financing activities
Repayment of finance lease		(0.4)	(0.3)
Cancellation of shares to cover employees' tax withholdings upon vesting of non-vested shares		(4.3)	(5.0)
Repurchase of common stock		(12.5)	(18.5)
Cash dividends and dividend equivalents paid		(11.3)	(10.2)
Net cash used in financing activities	[1]	(28.5)	(34.0)
Net increase (decrease) in cash, cash equivalents and restricted cash during the period		42.5	(10.2)
Cash, cash equivalents and restricted cash at beginning of period		278.6	139.6
Cash, cash equivalents and restricted cash at end of period		$ 321.1	$ 129.4

[1] See Note 12 for supplemental cash flow information.