Property and Equipment, Net - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense related to property and equipment	$ 2.8	$ 2.3	$ 6.0	$ 4.6
Property and equipment under capital lease	3.2		3.2		3.2
Accumulated depreciation related to assets under capital lease	2.4		2.4		2.1
Internal-use software development costs capitalized	0	2.8	0	5.0
Carrying value of internal-use software, net of accumulated amortization	11.1		11.1		13.6
Amortization of capitalized costs related to internal-use software	$ 1.3	$ 0.6	$ 2.5	$ 1.3

For each income statement presented, the amount charged to expense for amortization of capitalized computer software costs.

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The carrying amount of capitalized computer software costs net of accumulated amortization as of the balance sheet date.

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- Definition

Property, plant, or equipment held under lease agreements classified as an asset.

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- Definition

The total charge for the use of long-lived depreciable assets subject to a lease meeting the criteria for capitalization.

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- Definition

The current period expense charged against earnings on long-lived, physical assets not used in production, and which are not intended for resale, to allocate or recognize the cost of such assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset; or to reflect consumption during the period of an asset that is not used in production.

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