Acquisitions (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended		0 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2012	Nov. 17, 2010 Servicio Pan Americano de Proteccion, S.A. de C.V.[Member] Provisional [Member]	Nov. 17, 2010 Servicio Pan Americano de Proteccion, S.A. de C.V.[Member] Adustments [Member]	Nov. 17, 2010 Servicio Pan Americano de Proteccion, S.A. de C.V.[Member] Final [Member]	Dec. 23, 2010 Threshold [Member] Provisional [Member]	Dec. 23, 2010 Threshold [Member] Adustments [Member]	Dec. 23, 2010 Threshold [Member] Final [Member]
Fair Value of Purchase Consideration [Abstract]
Cash Paid for Acquired Entity				$ 17.0	$ 59.8	$ (1.1)	$ 58.7
Fair value of noncontrolling interest					0.1	(0.1)	0
Fair value of the previously held noncontrolling interest					9.7	0	9.7
Fair value of purchase consideration					69.6	(1.2)	68.4
Purchase Price Allocation [Abstract]
Cash					12.2	(0.1)	12.1	0.5	0	0.5
Accounts receivable					58.8	0	58.8	5.0	0	5.0
Other current assets					12.3	(0.9)	11.4	2.5	0	2.5
Property and equipment, net					106.4	0	106.4	10.6	5.8	16.4
Indefinite-lived intangible asset					12.1	0	12.1	16.3	(5.1)	11.2
Goodwill								12.9	0.4	13.3
Other noncurrent assets					18.7	0	18.7
Current liabilities					(75.1)	(0.8)	(75.9)	(4.2)	(0.8)	(5.0)
Noncurrent liabilities					(70.7)	2.7	(68.0)	(4.8)	(0.3)	(5.1)
Fair value of net assets acquired					74.7	0.9	75.6	38.8	0	38.8
Fair value of purchase consideration					69.6	(1.2)	68.4
Bargain purchase gain	$ 2.1	$ 5.1	$ 0		$ 5.1	$ 2.1	$ 7.2

Amount of cash paid to acquire the entity.

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The total cost of the acquired entity including the cash paid to shareholders of acquired entities, fair value of debt and equity securities issued to shareholders of acquired entities, the fair value of the liabilities assumed, and direct costs of the acquisition.

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The total purchase price of the acquired entity. This includes cash paid to equity interest holders of the acquired entity, fair value of debt and equity securities issued to equity holders of the acquired entity, and transaction costs paid to third parties to consummate the acquisition.

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The amount of cash and cash equivalents acquired in a business combination.

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The amount of acquisition cost of a business combination allocated to prepaid expenses and other current assets. Does not include amounts allocated to cash and cash equivalents, marketable securities, receivables, inventory, and assets not to be used.

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The amount of acquisition cost of a business combination allocated to receivables.

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The amount of acquisition cost of a business combination allocated to current liabilities of the acquired entity.

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Amount of goodwill arising from a business combination, which is the excess of the cost of the acquired entity over the amounts assigned to assets acquired and liabilities assumed.

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The amount of acquisition cost of a business combination allocated to an identifiable intangible asset that will not be amortized. Does not include goodwill.

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The amount of acquisition cost of a business combination allocated to noncurrent liabilities of the acquired entity.

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The amount of acquisition cost of a business combination allocated to noncurrent assets of the acquired entity, except for property plant and equipment, intangible assets, and goodwill.

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The amount of acquisition cost of a business combination allocated to property, plant and equipment to be used in ongoing operations.

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This element represents the fair value of the noncontrolling interest in the acquiree at the acquisition date.

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In a business combination in which the amount of net identifiable assets acquired and liabilities assumed exceeds the aggregate consideration transferred or to be transferred (as defined), this element represents the amount of gain recognized by the entity.

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In a business combination achieved in stages, this element represents the acquisition-date fair value of the equity interest in the acquiree held by the acquirer immediately before the acquisition date.

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