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Effect of New Accounting Pronouncements - Additional Information (Detail) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2017 | Sep. 30, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Income tax benefit recognized | $ (41.1) | $ (35.5) | $ (90.0) | $ (55.9)
Reclassification of payments from investing activities to operating activities |  |  | 459.1 | 368.9
Reclassification of payments from investing activities to financing activities |  |  | $ (46.6) | (10.1)
Description of contracts renewal period |  |  | One year or less |
Restatement Adjustment [Member] |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Reclassification of payments from investing activities to operating activities |  |  |  | 19.5
Reclassification of payments from investing activities to financing activities |  |  |  | 41.7
Accounting Standards Update 2016-09 [Member] |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Income tax benefit recognized | $ 1.8 | $ 1.7 | $ 11.9 | $ 4.8

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