CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 10.3	$ 122.8
Adjustments to reconcile net income to net cash provided by operations:
Depreciation and amortization	99.1	98.9
Deferred income taxes	16.8	(12.6)
Provision for pension and other postretirement benefits	2.5	4.8
Share-based compensation expense	6.8	8.2
Loss on disposals of property and equipment	3.4	2.2
Other	0.2	0.0
Changes in current assets and liabilities:
Receivables - trade and other	(22.2)	(16.4)
Prepaid expenses and other current assets	(1.2)	6.8
Accounts payable	3.4	(17.2)
Accrued income taxes	2.3	5.2
Other current liabilities	(17.1)	(28.1)
Other postretirement benefit claims paid	(0.9)	(3.0)
Contributions to pension plans	(5.9)	(3.1)
Deferred revenues	(6.3)	(2.5)
Net changes in other noncurrent assets and liabilities	(9.7)	(3.1)
Net cash provided by operating activities	81.5	162.9
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(30.9)	(32.9)
Proceeds from disposals of property and equipment	0.1	0.3
Net cash used in investing activities	(30.8)	(32.6)
CASH FLOWS FROM FINANCING ACTIVITIES:
Reductions of long-term debt	(127.7)	(16.5)
Shares repurchased for tax withholdings on vesting of restricted share units	(5.3)	(2.8)
Net cash used in financing activities	(133.0)	(19.3)
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(82.3)	111.0
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	1,255.5	484.2
CASH AND CASH EQUIVALENTS, END OF PERIOD	$ 1,173.2	$ 595.2