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Borrowings - Additional Information (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018 | Dec. 31, 2018
Debt Instrument [Line Items] |  |  |  |  |
Debt and capital lease obligations | $ 200,000 |  | $ 200,000 |  | $ 200,000
Interest Rate Per Annum |  |  |  |  | 4.29%
Interest expense | 2,600 | $ 2,700 | 7,900 | $ 8,000 |
Level 2 |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Borrowings fair value | 203,200 |  | 203,200 |  |
Series B | Senior notes |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Debt and capital lease obligations | 0 |  | 0 |  | $ 50,000
Interest Rate Per Annum |  |  |  |  | 5.32%
Series E | Senior notes |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Debt and capital lease obligations | $ 50,000 |  | $ 50,000 |  | $ 0
Interest Rate Per Annum | 4.53% |  | 4.53% |  |

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- Definition Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13433-108611 + Details
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