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Fixed Assets - Summary of Fixed Assets (Detail) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017
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Property Plant and Equipment Useful Life and Values [Abstract] |  |  |
Office equipment | $ 30.0 | $ 28.6 |
Furniture and fixtures | 116.9 | 112.3 |
Leasehold improvements | 132.1 | 124.2 |
Computer equipment | 145.1 | 147.9 |
Land and buildings - corporate headquarters | 144.3 | 143.6 |
Software | 346.0 | 291.9 |
Other | 12.4 | 12.0 |
Work in process | 14.9 | 20.1 |
Gross fixed assets | 941.7 | 880.6 |
Accumulated depreciation | (504.8) | (468.4) |
Net fixed assets | $ 436.9 | $ 412.2 | [1]
[1] | See Note 3 - Revenues from Contracts with Customers for additional information about the restatements related to Topic 606.

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- Definition Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.14) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Amount before accumulated amortization of capitalized costs for computer software, including but not limited to, acquired and internally developed computer software. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 985 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756 + Details
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- Definition Amount of structure or a modification to a structure under construction. Includes recently completed structures or modifications to structures that have not been placed into service. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 + Details
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