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Acquisitions - Business Acquisition, Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Millions | 3 Months Ended
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Mar. 31, 2018 | Mar. 31, 2017
Business Combinations [Abstract] |  |
Pro Forma Acquisition Expenses, Net of Tax | $ 0.5 |
Interest income | 107.6 | $ 100.1
Non-interest income | 35.2 | 36.6
Total revenues | 142.8 | 136.7
Net income | $ 35.9 | $ 29.2
EPS - basic (in dollars per share) | $ 0.63 | $ 0.52
EPS - diluted (in dollars per share) | $ 0.63 | $ 0.52

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- Definition The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(2)-(3) -URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463 + Details
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