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Net Income Per Share and Stockholders' Equity, Narrative (Details) - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2018 | Mar. 31, 2017
Earnings Per Share [Abstract] |  |
Payments of Dividends | $ 10.0 | $ 9.3
Stock Repurchase Program, Remaining Authorized Repurchase Amount | $ 104.5 |

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- Definition Cash outflow in the form of capital distributions and dividends to common shareholders, preferred shareholders and noncontrolling interests. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3291-108585 + Details
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- Definition Amount remaining of a stock repurchase plan authorized. + References No definition available. + Details
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