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Acquisitions - Business Acquisition Pro Forma Information (Details) $ / shares in Units, $ in Thousands | 3 Months Ended
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Mar. 31, 2018 USD ($) $ / shares
Business Combinations [Abstract] |
Net sales | $ 434,526
Income before income taxes | 81,924
Net income | $ 63,933
Net income per share — basic (in dollars per share) | $ / shares | $ 2.57
Net income per share — diluted (in dollars per share) | $ / shares | $ 2.53

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