Condensed Consolidating Financial Information - Condensed Consolidating Statement of Cash Flows (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018
Condensed Statements of Cash Flows, Captions [Line Items]
Net cash flow provided by (used for) operating activities	$ 162.1	$ 137.4
Capital expenditures	(65.4)	(62.1)
Acquisitions	(60.7)	(5.6)
MTA franchise rights	(16.9)	(9.4)
Net proceeds from dispositions	4.9	6.0
Net cash flow provided by (used for) investing activities	(138.1)	(71.1)
Proceeds from long-term debt borrowings	760.0	89.0
Repayments of long-term debt borrowings	(695.0)	(79.0)
Proceeds from borrowings under short-term debt facilities	280.0	200.0
Repayments of borrowings under short-term debt facilities	(230.0)	(105.0)
Payments of deferred financing costs	(9.5)	(0.2)
Payment of debt extinguishment charges	(7.4)	0.0
Proceeds from shares issued under the ATM Program	50.9	0.0
Taxes withheld for stock-based compensation	(7.7)	(8.2)
Dividends	(156.0)	(152.9)
Intercompany	0.0	0.0
Net cash flow provided by (used for) financing activities	(14.7)	(56.3)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	0.3	(0.2)
Net increase (decrease) in cash, cash equivalents and restricted cash	9.6	9.8
Cash, cash equivalents and restricted cash, beginning of period	54.1	48.3
Cash, cash equivalents and restricted cash, end of period	63.7	58.1
Eliminations
Condensed Statements of Cash Flows, Captions [Line Items]
Net cash flow provided by (used for) operating activities	0.0	0.0
Capital expenditures	0.0	0.0
Acquisitions	0.0	0.0
MTA franchise rights	0.0	0.0
Net proceeds from dispositions	0.0	0.0
Net cash flow provided by (used for) investing activities	0.0	0.0
Proceeds from long-term debt borrowings	0.0	0.0
Repayments of long-term debt borrowings	0.0	0.0
Proceeds from borrowings under short-term debt facilities	0.0	0.0
Repayments of borrowings under short-term debt facilities	0.0	0.0
Payments of deferred financing costs	0.0	0.0
Payment of debt extinguishment charges	0.0
Proceeds from shares issued under the ATM Program	0.0
Taxes withheld for stock-based compensation	0.0	0.0
Dividends	0.0	0.0
Intercompany	0.0	0.0
Net cash flow provided by (used for) financing activities	0.0	0.0
Effect of exchange rate changes on cash, cash equivalents and restricted cash	0.0	0.0
Net increase (decrease) in cash, cash equivalents and restricted cash	0.0	0.0
Cash, cash equivalents and restricted cash, beginning of period	0.0	0.0
Cash, cash equivalents and restricted cash, end of period	0.0	0.0
Parent Company
Condensed Statements of Cash Flows, Captions [Line Items]
Net cash flow provided by (used for) operating activities	(1.2)	(1.2)
Capital expenditures	0.0	0.0
Acquisitions	0.0	0.0
MTA franchise rights	0.0	0.0
Net proceeds from dispositions	0.0	0.0
Net cash flow provided by (used for) investing activities	0.0	0.0
Proceeds from long-term debt borrowings	0.0	0.0
Repayments of long-term debt borrowings	0.0	0.0
Proceeds from borrowings under short-term debt facilities	0.0	0.0
Repayments of borrowings under short-term debt facilities	0.0	0.0
Payments of deferred financing costs	0.0	0.0
Payment of debt extinguishment charges	0.0
Proceeds from shares issued under the ATM Program	50.9
Taxes withheld for stock-based compensation	0.0	0.0
Dividends	(154.5)	(150.9)
Intercompany	104.8	152.1
Net cash flow provided by (used for) financing activities	1.2	1.2
Effect of exchange rate changes on cash, cash equivalents and restricted cash	0.0	0.0
Net increase (decrease) in cash, cash equivalents and restricted cash	0.0	0.0
Cash, cash equivalents and restricted cash, beginning of period	0.0	0.0
Cash, cash equivalents and restricted cash, end of period	0.0	0.0
Subsidiary Issuer
Condensed Statements of Cash Flows, Captions [Line Items]
Net cash flow provided by (used for) operating activities	(84.4)	(74.5)
Capital expenditures	0.0	0.0
Acquisitions	0.0	0.0
MTA franchise rights	0.0	0.0
Net proceeds from dispositions	0.0	0.0
Net cash flow provided by (used for) investing activities	0.0	0.0
Proceeds from long-term debt borrowings	760.0	89.0
Repayments of long-term debt borrowings	(695.0)	(79.0)
Proceeds from borrowings under short-term debt facilities	0.0	0.0
Repayments of borrowings under short-term debt facilities	0.0	0.0
Payments of deferred financing costs	(9.3)	(0.1)
Payment of debt extinguishment charges	(7.4)
Proceeds from shares issued under the ATM Program	0.0
Taxes withheld for stock-based compensation	0.0	0.0
Dividends	0.0	0.0
Intercompany	31.3	74.3
Net cash flow provided by (used for) financing activities	79.6	84.2
Effect of exchange rate changes on cash, cash equivalents and restricted cash	0.0	0.0
Net increase (decrease) in cash, cash equivalents and restricted cash	(4.8)	9.7
Cash, cash equivalents and restricted cash, beginning of period	12.0	10.2
Cash, cash equivalents and restricted cash, end of period	7.2	19.9
Guarantor Subsidiaries
Condensed Statements of Cash Flows, Captions [Line Items]
Net cash flow provided by (used for) operating activities	227.4	216.2
Capital expenditures	(59.8)	(52.5)
Acquisitions	(60.7)	(5.6)
MTA franchise rights	(16.9)	(9.4)
Net proceeds from dispositions	4.9	5.7
Net cash flow provided by (used for) investing activities	(132.5)	(61.8)
Proceeds from long-term debt borrowings	0.0	0.0
Repayments of long-term debt borrowings	0.0	0.0
Proceeds from borrowings under short-term debt facilities	90.0	75.0
Repayments of borrowings under short-term debt facilities	(75.0)	0.0
Payments of deferred financing costs	(0.2)	0.0
Payment of debt extinguishment charges	0.0
Proceeds from shares issued under the ATM Program	0.0
Taxes withheld for stock-based compensation	(7.7)	(8.2)
Dividends	0.0	0.0
Intercompany	(96.7)	(216.2)
Net cash flow provided by (used for) financing activities	(89.6)	(149.4)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	0.0	0.0
Net increase (decrease) in cash, cash equivalents and restricted cash	5.3	5.0
Cash, cash equivalents and restricted cash, beginning of period	1.4	3.7
Cash, cash equivalents and restricted cash, end of period	6.7	8.7
Non-Guarantor Subsidiaries
Condensed Statements of Cash Flows, Captions [Line Items]
Net cash flow provided by (used for) operating activities	20.3	(3.1)
Capital expenditures	(5.6)	(9.6)
Acquisitions	0.0	0.0
MTA franchise rights	0.0	0.0
Net proceeds from dispositions	0.0	0.3
Net cash flow provided by (used for) investing activities	(5.6)	(9.3)
Proceeds from long-term debt borrowings	0.0	0.0
Repayments of long-term debt borrowings	0.0	0.0
Proceeds from borrowings under short-term debt facilities	190.0	125.0
Repayments of borrowings under short-term debt facilities	(155.0)	(105.0)
Payments of deferred financing costs	0.0	(0.1)
Payment of debt extinguishment charges	0.0
Proceeds from shares issued under the ATM Program	0.0
Taxes withheld for stock-based compensation	0.0	0.0
Dividends	(1.5)	(2.0)
Intercompany	(39.4)	(10.2)
Net cash flow provided by (used for) financing activities	(5.9)	7.7
Effect of exchange rate changes on cash, cash equivalents and restricted cash	0.3	(0.2)
Net increase (decrease) in cash, cash equivalents and restricted cash	9.1	(4.9)
Cash, cash equivalents and restricted cash, beginning of period	40.7	34.4
Cash, cash equivalents and restricted cash, end of period	$ 49.8	$ 29.5

The net change during the reporting period in intercompany amounts.

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Purchase Of MTA Franchise Rights

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Amount of cash and cash equivalents, and cash and cash equivalents restricted to withdrawal or usage. Excludes amount for disposal group and discontinued operations. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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