Statements of Cash Flows - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Operating Activities
Net income		$ 59.1	$ 52.2
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		18.6	16.2
Deferred income taxes		(13.5)	15.7
Other adjustments for non-cash items		(0.1)	0.2
Changes in operating assets and liabilities		124.2	53.8
Net cash provided by operating activities		188.3	138.1
Investing Activities
Property, plant and equipment purchased		(50.7)	(35.0)
Other		(0.5)	0.3
Net cash used in investing activities		(51.2)	(34.7)
Financing Activities
Repayment of short-term debt, net		(30.2)	(53.0)
Repayment of long-term debt		(70.0)
Repayment of affiliated current borrowings, net		(41.1)	(48.0)
Other		(1.0)
Net cash used in financing activities		(142.3)	(101.0)
Increase (decrease) in cash and equivalents		(5.2)	2.4
Cash, restricted cash and equivalents at beginning of period	[1]	6.7	7.6
Cash, restricted cash and equivalents at end of period	[1]	1.5	10.0
Significant noncash investing activities:
Accrued capital expenditures		$ 5.5	$ 11.5

[1] No amounts were held in restricted cash and equivalents in any of the periods presented