Supplemental Guarantor Information HY Condensed Consolidating Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Consolidating Balance Sheets HY
Cash and cash equivalents	$ 9.7	$ 7.4	$ 57.9	$ 4.6
Other Assets, Current	3.9	2.2
Assets, Current	229.9	200.4
Property, plant and equipment, net	1,085.5	975.5
Investment in CyrusOne	128.0	55.5
Goodwill	14.3	14.3
Other Assets, Noncurrent	18.8	17.8
Assets	1,541.0	1,446.4
Current portion of long-term debt	7.5	13.8
Accounts payable	105.9	128.9
Other Liabilities, Current	31.9	25.0
Disposal Group, Including Discontinued Operation, Other Liabilities, Current	0.0	5.4
Liabilities, Current	232.9	259.2
Long-term debt, less current portion	1,199.1	1,223.8
Other Liabilities, Noncurrent	33.0	36.6
Liabilities	1,662.7	1,744.6
Stockholders' Equity Attributable to Parent	(121.7)	(298.2)	(648.5)	(676.7)
Liabilities and Equity	1,541.0	1,446.4
Notes guaranteed by subsidiaries [Member]
Condensed Consolidating Balance Sheets HY
Cash and cash equivalents	9.7	7.4	57.9	4.6
Receivables, Net, Current	178.6	157.1
Other Assets, Current	41.6	35.9
Assets, Current	229.9	200.4
Property, plant and equipment, net	1,085.5	975.5
Investment in CyrusOne	128.0	55.5
Goodwill	14.3	14.3
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0.0	0.0
Other Assets, Noncurrent	83.3	200.7
Assets	1,541.0	1,446.4
Current portion of long-term debt	7.5	13.8
Accounts payable	105.9	128.9
Other Liabilities, Current	119.5	111.1
Disposal Group, Including Discontinued Operation, Other Liabilities, Current	0.0	5.4
Liabilities, Current	232.9	259.2
Long-term debt, less current portion	1,199.1	1,223.8
Other Liabilities, Noncurrent	230.7	261.6
Due to Related Parties, Noncurrent	0.0	0.0
Liabilities	1,662.7	1,744.6
Stockholders' Equity Attributable to Parent	(121.7)	(298.2)
Liabilities and Equity	1,541.0	1,446.4
Notes guaranteed by subsidiaries [Member] | Consolidation, Eliminations [Member]
Condensed Consolidating Balance Sheets HY
Cash and cash equivalents	0.0	0.0	0.0	0.0
Receivables, Net, Current	0.0	0.0
Other Assets, Current	0.0	0.0
Assets, Current	0.0	0.0
Property, plant and equipment, net	0.0	0.0
Investment in CyrusOne	0.0	0.0
Goodwill	0.0	0.0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	(1,788.9)	(1,680.6)
Other Assets, Noncurrent	(144.8)	(146.2)
Assets	(1,933.7)	(1,826.8)
Current portion of long-term debt	0.0	0.0
Accounts payable	0.0	0.0
Other Liabilities, Current	0.0	0.0
Disposal Group, Including Discontinued Operation, Other Liabilities, Current	0.0	0.0
Liabilities, Current	0.0	0.0
Long-term debt, less current portion	0.0	0.0
Other Liabilities, Noncurrent	(144.8)	(146.2)
Due to Related Parties, Noncurrent	(147.7)	(180.4)
Liabilities	(292.5)	(326.6)
Stockholders' Equity Attributable to Parent	(1,641.2)	(1,500.2)
Liabilities and Equity	(1,933.7)	(1,826.8)
Notes guaranteed by subsidiaries [Member] | Parent Company [Member]
Condensed Consolidating Balance Sheets HY
Cash and cash equivalents	7.8	4.6	56.2	2.1
Receivables, Net, Current	17.8	0.7
Other Assets, Current	1.1	1.6
Assets, Current	26.7	6.9
Property, plant and equipment, net	0.3	0.3
Investment in CyrusOne	0.0	0.0
Goodwill	0.0	0.0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	816.7	844.6
Other Assets, Noncurrent	179.1	207.2
Assets	1,022.8	1,059.0
Current portion of long-term debt	0.0	5.4
Accounts payable	0.7	0.7
Other Liabilities, Current	42.9	41.6
Disposal Group, Including Discontinued Operation, Other Liabilities, Current	0.0	0.0
Liabilities, Current	43.6	47.7
Long-term debt, less current portion	960.3	1,018.6
Other Liabilities, Noncurrent	207.9	235.5
Due to Related Parties, Noncurrent	0.0	54.7
Liabilities	1,211.8	1,356.5
Stockholders' Equity Attributable to Parent	(189.0)	(297.5)
Liabilities and Equity	1,022.8	1,059.0
Notes guaranteed by subsidiaries [Member] | Guarantor Subsidiaries [Member]
Condensed Consolidating Balance Sheets HY
Cash and cash equivalents	0.3	0.4	0.2	0.3
Receivables, Net, Current	1.7	2.8
Other Assets, Current	17.9	13.9
Assets, Current	19.9	17.1
Property, plant and equipment, net	54.4	53.4
Investment in CyrusOne	128.0	55.5
Goodwill	12.1	12.1
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	972.2	772.1
Other Assets, Noncurrent	43.9	132.6
Assets	1,230.5	1,042.8
Current portion of long-term debt	2.5	3.4
Accounts payable	33.1	42.8
Other Liabilities, Current	22.5	23.9
Disposal Group, Including Discontinued Operation, Other Liabilities, Current	0.0	5.4
Liabilities, Current	58.1	75.5
Long-term debt, less current portion	51.1	53.3
Other Liabilities, Noncurrent	0.7	3.8
Due to Related Parties, Noncurrent	0.0	0.0
Liabilities	109.9	132.6
Stockholders' Equity Attributable to Parent	1,120.6	910.2
Liabilities and Equity	1,230.5	1,042.8
Notes guaranteed by subsidiaries [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Consolidating Balance Sheets HY
Cash and cash equivalents	1.6	2.4	$ 1.5	$ 2.2
Receivables, Net, Current	159.1	153.6
Other Assets, Current	22.6	20.4
Assets, Current	183.3	176.4
Property, plant and equipment, net	1,030.8	921.8
Investment in CyrusOne	0.0	0.0
Goodwill	2.2	2.2
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0.0	63.9
Other Assets, Noncurrent	5.1	7.1
Assets	1,221.4	1,171.4
Current portion of long-term debt	5.0	5.0
Accounts payable	72.1	85.4
Other Liabilities, Current	54.1	45.6
Disposal Group, Including Discontinued Operation, Other Liabilities, Current	0.0	0.0
Liabilities, Current	131.2	136.0
Long-term debt, less current portion	187.7	151.9
Other Liabilities, Noncurrent	166.9	168.5
Due to Related Parties, Noncurrent	147.7	125.7
Liabilities	633.5	582.1
Stockholders' Equity Attributable to Parent	587.9	589.3
Liabilities and Equity	$ 1,221.4	$ 1,171.4