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Commitments and Contingencies (Narrative) (Details) $ in Thousands | 12 Months Ended
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Dec. 31, 2018 USD ($) Lawsuit | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($)
Commitments and Contingencies Disclosure [Abstract] |  |  |
Rent expense | $ | $ 34,679 | $ 32,619 | $ 28,016
Loss Contingencies [Line Items] |  |  |
Number of lawsuits filed | 7 |  |
Cases with SPTC as Defendant |  |  |
Loss Contingencies [Line Items] |  |  |
Number of lawsuits filed | 4 |  |
Claims for Violations of Louisiana Racketeering Act |  |  |
Loss Contingencies [Line Items] |  |  |
Number of lawsuits filed | 2 |  |
Cases Remaining in Parish of East Baton Rouge Granted Indefinite Extensions to Respond |  |  |
Loss Contingencies [Line Items] |  |  |
Number of lawsuits filed | 2 |  |
Cases Filed in East Baton Rouge |  |  |
Loss Contingencies [Line Items] |  |  |
Number of lawsuits filed | 2 |  |

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