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Income Taxes (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2018 | Mar. 31, 2017 | Dec. 31, 2017
Operating Loss Carryforwards [Line Items] |  |  |
Federal tax rate, percent | 21.00% |  | 35.00%
Income tax benefit from the Tax Act |  |  | $ 39,300
Income tax provision | $ 20,633 | $ 26,846 |
Effective income tax rates | 27.60% | 37.80% |
Actual income tax rates | 27.00% | 33.60% |
Unrecognized income tax benefits | $ 800 |  | 800
Accrued interest expense related to unrecognized income tax benefits | 100 |  | 100
Interest income related to unrecognized income tax benefits |  | $ 400 |
Interest expense related to unrecognized income tax benefits | 100 |  |
Unrecognized tax benefits, decrease resulting from settlements with taxing authorities |  | $ 3,300 |
Other Long-term Liabilities [Member] |  |  |
Operating Loss Carryforwards [Line Items] |  |  |
Income tax reserves | $ 900 |  | $ 900

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- Definition Carrying amount as of the balance sheet date of the unpaid sum of the known and estimated amounts payable to satisfy all domestic and foreign income tax obligations due beyond one year or the operating cycle, whichever is longer. Alternate captions include income taxes payable, noncurrent. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(15)(1)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(15)(b)(1)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(24)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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