Condensed Consolidated Statements of Comprehensive Income Parenthetical - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Unrealized gains on Investment in CyrusOne, tax	$ 0.0	$ 0.0	$ 0.0	$ 4.4
Reclassification adjustment for gain on sale of Investment in CyrusOne included in net income, tax	0.0	0.0	0.0	(41.3)
Unrealized loss on cash flow hedge arising during the period, tax	(0.4)	0.0	(0.4)	0.0
Amortization of prior service benefits included in net income, tax	(0.2)	(0.4)	(0.4)	(0.8)
Amortization of net actuarial loss included in net income, tax	$ 1.2	$ 2.0	$ 2.4	$ 4.0

Amount of tax (expense) benefit of reclassification adjustment from accumulated other comprehensive (income) loss for prior service cost (credit) of defined benefit plan.

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Amount, before reclassification, of tax expense (benefit) for gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=114867106&loc=d3e640-108580

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Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

+ References

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Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan.

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Amount of tax expense (benefit) before reclassification adjustments of unrealized holding gain (loss) on available-for-sale securities.

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-Publisher FASB
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