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Acquisition of Business - Narrative on Acquisition of Subsidiary (Details) - National Interstate $ / shares in Units, $ in Millions | Nov. 10, 2016 USD ($) $ / shares
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Business Acquisition |
Percentage ownership of National Interstate by noncontrolling owners prior to acquisition | 49.00%
Payments to acquire additional interest in subsidiaries | $ | $ 315
Acquisition price per share (USD per share) | $ 32.00
Cash dividend paid (USD per share) | $ 0.50

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- Definition Aggregate dividends paid during the period for each share of common stock outstanding. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 + Details
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