Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Flows from Operating Activities:
Net income	$ 47.0	$ 103.5	$ 59.5
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	141.6	128.2	114.2
Deferred income tax (benefit) expense	(3.4)	(87.2)	3.1
Payments in excess of expense for postretirement plan benefits	(2.4)	(1.8)	(2.6)
Share-based compensation expense	3.1	4.8	6.5
Loss (gain) on extinguishment of debt, net	0.3	20.4	(25.0)
Loss on divestiture of business	0.0	0.0	14.7
Loss from equity method investment	5.4	0.0	0.0
Changes in working capital pertaining to operating activities (net of the effects of divestiture):
Receivables	(6.9)	(7.8)	3.7
Inventories	0.6	(18.5)	29.4
Accounts payable	(0.7)	11.7	(0.8)
Accrued liabilities	(7.3)	2.6	6.8
Deferred revenue	1.3	(0.8)	0.4
Interest payable	(1.8)	(10.8)	(2.7)
Income taxes	4.5	(0.2)	7.0
Other	4.5	4.4	4.9
Net cash provided by operating activities	185.8	148.5	219.1
Cash Flows from Investing Activities:
Capital expenditures	(100.3)	(75.6)	(63.7)
Return of Brazilian investment	0.0	20.5	20.5
Divestiture of coal business	0.0	0.0	(12.8)
Sale of equity method investment	4.0	0.0	0.0
Other investing activities	0.5	0.0	2.1
Net cash used in investing activities	(95.8)	(55.1)	(53.9)
Cash Flows from Financing Activities:
Proceeds from issuance of long-term debt	45.0	693.7	0.0
Repayment of long-term debt	(45.7)	(644.9)	(66.1)
Debt issuance costs	(0.5)	(17.4)	(0.2)
Proceeds from revolving facility	179.5	350.0	28.0
Repayment of revolving facility	(204.5)	(392.0)	(98.4)
Proceeds from financing obligation	0.0	0.0	16.2
Repayment of financing obligation	(2.6)	(2.5)	(1.0)
Cash distributions to noncontrolling interests	(31.9)	(47.0)	(49.4)
Acquisition of additional interest in the Partnership	(4.2)	(48.7)	0.0
Other financing activities	0.4	1.1	(1.4)
Net cash used in financing activities	(64.5)	(107.7)	(172.3)
Net increase (decrease) in cash, cash equivalents and restricted cash	25.5	(14.3)	(7.1)
Cash, cash equivalents and restricted cash at beginning of year	120.2	134.5	141.6
Cash, cash equivalents and restricted cash at end of year	145.7	120.2	134.5
Supplemental Disclosure of Cash Flow Information
Interest paid, net of capitalized interest of $3.2 million, $1.1 million and $5.0 million, respectively	59.6	67.9	53.4
Income taxes paid, net of refunds of $4.3 million, $1.0 million and $8.2 million, respectively	$ 3.7	$ 5.8	$ (2.3)