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Business Combinations - Summary of Unaudited Pro Forma Historical Results (Detail) - USD ($) $ / shares in Units, $ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016
Business Combinations [Abstract] |  |
Total revenues | $ 6,222.8 | $ 5,765.9
Net earnings attributable to controlling interests | $ 466.3 | $ 414.5
Basic earnings per share | $ 2.58 | $ 2.33
Diluted earnings per share | $ 2.56 | $ 2.31

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