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Stockholders’ Equity and Earnings Per Share (Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Income tax benefits due to ASU 2016-09 | $ 4.8 |
Accounting Standards Update 2016-09 |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Income tax benefits due to ASU 2016-09 (in dollars per share) | $ 0.03 |
RSAs |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Shares outstanding (in shares) | 0 | 0

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- Definition Amount of the effect of a change in accounting principle on basic earnings per share. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=64853466&loc=d3e22499-107794 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=64853466&loc=d3e22580-107794 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=64853466&loc=d3e22583-107794 + Details
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