Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities
Net income (loss)	$ 102.1	$ 353.7	$ 75.6
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	182.2	170.2	231.0
Loss on extinguishment of debt	19.0	20.9	19.6
Gain on sale of CyrusOne investment	(157.0)	(449.2)	(192.8)
Impairment of assets	0.0	0.0	12.1
Provision for loss on receivables	9.4	8.5	10.4
Noncash portion of interest expense	3.3	4.6	6.2
Deferred income tax expense, including valuation allowance change	59.4	184.5	47.4
Pension and other postretirement payments in excess of expense	(8.3)	(11.5)	(25.7)
Deferred gain on sale of wireless spectrum licenses - discontinued operations	0.0	(112.6)	0.0
Amortization of deferred gain - discontinued operations	0.0	(6.5)	(22.9)
Stock-based compensation	5.1	4.1	3.3
Gain on transfer of lease obligations - discontinued operations	0.0	(15.9)	0.0
Other, net	(3.7)	3.1	10.5
Changes in operating assets and liabilities, net of effects of divestitures:
Increase in receivables	(18.3)	(1.9)	(23.7)
(Increase) decrease in inventory, materials, supplies, prepaid expenses and other current assets	(6.2)	3.6	(7.2)
(Decrease) increase in accounts payable	(13.1)	(17.0)	38.7
Decrease in accrued and other current liabilities	(3.0)	(30.6)	(0.8)
(Increase) decrease in other noncurrent assets	(1.3)	1.5	0.7
Increase (decrease) in other noncurrent liabilities	3.6	1.4	(7.2)
Net cash provided by operating activities	173.2	110.9	175.2
Cash flows from investing activities
Capital expenditures	(286.4)	(283.6)	(182.3)
Proceeds from sale of CyrusOne investment	189.7	643.9	355.9
Dividends received from CyrusOne (equity method investment)	2.1	22.2	28.4
Proceeds from sale of wireless spectrum licenses	0.0	0.0	194.4
Other, net	(0.9)	0.7	(3.8)
Net cash (used in) provided by investing activities	(95.5)	383.2	392.6
Cash flows from financing activities
Proceeds from issuance of long-term debt	635.0	0.0	0.0
Net increase (decrease) in corporate credit and receivables facilities with initial maturities less than 90 days	71.9	(1.6)	(127.0)
Repayment of debt	(759.3)	(531.7)	(376.5)
Debt issuance costs	(11.1)	(0.4)	(0.9)
Dividends paid on preferred stock	(10.4)	(10.4)	(10.4)
Common stock repurchase	(4.8)	0.0	0.0
Other, net	3.3	(0.5)	0.3
Net cash used in financing activities	(75.4)	(544.6)	(514.5)
Net increase (decrease) in cash and cash equivalents	2.3	(50.5)	53.3
Cash and cash equivalents at beginning of year	7.4	57.9	4.6
Cash and cash equivalents at end of year	$ 9.7	$ 7.4	$ 57.9