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Quarterly Financial Data (Unaudited) (Details Textual) - USD ($) $ / shares in Units, $ in Millions | 3 Months Ended | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2017
Schedule Of Quarterly Financial Information [Line Items] |  |
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount | $ 7.8 | $ 7.8
Increase In Basic Earnings Per Share From Change In Enacted Tax Rate | $ 0.48 | $ 0.48
Increase In Diluted Earnings Per Share From Change In Enacted Tax Rate | $ 0.47 | $ 0.47

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- Definition Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations, attributable to increase (decrease) in the income tax rates. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 45 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=84176650&loc=d3e32059-109318 + Details
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