Finance Receivable Sale Agreements	12 Months Ended
Dec. 31, 2019
Transfers and Servicing [Abstract]
Finance Receivable Sale Agreements	NOTE 7 — FINANCE RECEIVABLE SALE AGREEMENTS In December 2016, the Company entered into a master purchase and sale agreement (the "Master Purchase and Sale Agreement" or "MPSA") and a master transfer agreement (the "2016 Master Transfer Agreement") pursuant to which it sells finance receivables meeting certain underwriting criteria to certain financing partners, including Ally Bank and Ally Financial (the "Ally Parties"). Through November 2017 under the Purchase and Sale Agreement and the 2016 Master Transfer Agreement, the Company could sell up to an aggregate of $375.0 million, and $292.2 million, respectively, in principal balances of finance receivables subject to adjustment as described in the respective agreements. On November 3, 2017, the Company amended its MPSA to increase the aggregate amount of principal balances of finance receivables it can sell from $375.0 million to $1.5 billion. On November 2, 2018, the Company amended the MPSA to, among other things and subject to the terms of the agreement, commit the purchaser to purchase up to a maximum of $1.25 billion of principal balances of finance receivables after the amendment date. Subsequently, on April 19, 2019, the Company amended the MPSA to, among other things and subject to the terms of the agreement, commit the purchaser to purchase up to a maximum of $1.0 billion of principal balances of finance receivables after the amendment date. During the years ended December 31, 2019 and 2018, the Company sold approximately $418.8 million and $733.4 million, respectively, in principal balances of finance receivables under the MPSA and had approximately $658.3 million of unused capacity as of December 31, 2019. On November 3, 2017, the Company terminated the remaining capacity under the 2016 Master Transfer Agreement and replaced this facility by entering into a new master transfer agreement (the "2017 Master Transfer Agreement") with a purchaser trust (the "2017 Purchaser Trust") under which the trust committed to purchase up to an aggregate of approximately $357.1 million in principal balances of finance receivables. On November 2, 2018, the Company amended the 2017 Master Transfer Agreement to, among other things and subject to the terms of the agreement, increase and extend the trust's commitment to purchase finance receivables from the Company. On August 7, 2018, in connection with a refinancing transaction discussed further below, the Company purchased finance receivables it had previously sold under the 2017 Master Transfer Agreement and simultaneously entered into a transfer agreement with a purchaser trust under which the trust immediately purchased such finance receivables from the Company. On December 21, 2018, the Company entered into a transfer agreement with a purchaser trust under which the trust purchased principal balances of finance receivables from the Company, a portion of which were related to a refinancing transaction, discussed further below (the "2018 Transfer Agreement"). On May 7, 2019, the Company purchased the certificate of the 2017 Purchaser Trust for $34.0 million, net of cash acquired. At the time of acquisition the trust assets included $139.7 million of finance receivables that the Company had previously sold to the trust under the 2017 Master Transfer Agreement, and its liabilities included $105.7 million in associated debt and other liabilities. In connection with the certificate purchase, the Company and Ally Bank entered into an Amended and Restated Loan and Security Agreement (the "A&R Loan and Security Agreement") pursuant to which Ally Bank agreed to provide a $350.0 million revolving credit facility (the "SART 2017-1 Credit Facility") to fund certain automotive finance receivables originated by the Company, as further described in Note 9 — Debt Instruments. During the year ended December 31, 2019, prior to the acquisition of the certificate in the trust, the Company sold approximately $139.3 million in principal balances of finance receivables under the 2017 Master Transfer Agreement. During the year ended December 31, 2018, the Company sold approximately $348.8 million in principal balances of finance receivables under the 2017 Master Transfer Agreement, and approximately $115.0 million in principal balances of finance receivables under the 2018 Transfer Agreement, excluding those that were part of the refinancing transactions described below. During the year ended December 31, 2019, prior to the certificate purchase, the Company also purchased finance receivables that it previously sold to the purchaser trust under the 2017 Master Transfer Agreement for a total price of approximately $127.7 million and immediately resold such finance receivables into a securitization transaction, which is described further in Note 8 — Securitizations and Variable Interest Entities. This transaction was entered into in connection with the securitization transaction and was entered into independently from the terms of the 2017 Master Transfer Agreement. The total gain related to finance receivables sold to financing partners under the MPSA, the 2016 Master Transfer Agreement, the 2017 Master Transfer Agreement, and to investors in securitization transactions discussed in Note 8 — Securitizations and Variable Interest Entities was approximately $137.3 million, $51.7 million, and $21.7 million during the years ended December 31, 2019, 2018, and 2017, respectively, which is included in other sales and revenues in the accompanying consolidated statements of operations. During the year ended December 31, 2018, the Company purchased finance receivables that it previously sold to a purchaser trust under the 2017 Master Transfer Agreement for a total price of approximately $387.4 million and immediately resold such finance receivables to other trusts with the same certificate holder for the same price under separate transfer agreements, one of which was the 2018 Transfer Agreement. Other than customary repurchase obligations, the Company is not obligated to, nor does it have a right to, purchase or sell finance receivables it has previously sold under the 2017 Master Transfer Agreement. These transactions completed in 2018 were entered into in connection with a refinancing by the trusts' certificate holder and were entered into independently from the terms of the 2017 Master Transfer Agreement. The Company received fees totaling approximately $6.3 million for structuring and participating in these transactions, which are included in other sales and revenues in the accompanying consolidated statements of operations.

In December 2016, the Company entered into a master purchase and sale agreement (the "Master Purchase and Sale Agreement" or "MPSA") and a master transfer agreement (the "2016 Master Transfer Agreement") pursuant to which it sells finance receivables meeting certain underwriting criteria to certain financing partners, including Ally Bank and Ally Financial

(the "Ally Parties"). Through November 2017 under the Purchase and Sale Agreement and the 2016 Master Transfer Agreement, the Company could sell up to an aggregate of $375.0 million, and $292.2 million, respectively, in principal balances of finance receivables subject to adjustment as described in the respective agreements.

On November 3, 2017, the Company amended its MPSA to increase the aggregate amount of principal balances of finance receivables it can sell from $375.0 million to $1.5 billion. On November 2, 2018, the Company amended the MPSA to, among other things and subject to the terms of the agreement, commit the purchaser to purchase up to a maximum of $1.25 billion of principal balances of finance receivables after the amendment date. Subsequently, on April 19, 2019, the Company amended the MPSA to, among other things and subject to the terms of the agreement, commit the purchaser to purchase up to a maximum of $1.0 billion of principal balances of finance receivables after the amendment date.

During the years ended December 31, 2019 and 2018, the Company sold approximately $418.8 million and $733.4 million, respectively, in principal balances of finance receivables under the MPSA and had approximately $658.3 million of unused capacity as of December 31, 2019.

On November 3, 2017, the Company terminated the remaining capacity under the 2016 Master Transfer Agreement and replaced this facility by entering into a new master transfer agreement (the "2017 Master Transfer Agreement") with a purchaser trust (the "2017 Purchaser Trust") under which the trust committed to purchase up to an aggregate of approximately $357.1 million in principal balances of finance receivables. On November 2, 2018, the Company amended the 2017 Master Transfer Agreement to, among other things and subject to the terms of the agreement, increase and extend the trust's commitment to purchase finance receivables from the Company.

On August 7, 2018, in connection with a refinancing transaction discussed further below, the Company purchased finance receivables it had previously sold under the 2017 Master Transfer Agreement and simultaneously entered into a transfer agreement with a purchaser trust under which the trust immediately purchased such finance receivables from the Company.

On December 21, 2018, the Company entered into a transfer agreement with a purchaser trust under which the trust purchased principal balances of finance receivables from the Company, a portion of which were related to a refinancing transaction, discussed further below (the "2018 Transfer Agreement").

On May 7, 2019, the Company purchased the certificate of the 2017 Purchaser Trust for $34.0 million, net of cash acquired. At the time of acquisition the trust assets included $139.7 million of finance receivables that the Company had previously sold to the trust under the 2017 Master Transfer Agreement, and its liabilities included $105.7 million in associated debt and other liabilities. In connection with the certificate purchase, the Company and Ally Bank entered into an Amended and Restated Loan and Security Agreement (the "A&R Loan and Security Agreement") pursuant to which Ally Bank agreed to provide a $350.0 million revolving credit facility (the "SART 2017-1 Credit Facility") to fund certain automotive finance receivables originated by the Company, as further described in Note 9 — Debt Instruments.

During the year ended December 31, 2019, prior to the acquisition of the certificate in the trust, the Company sold approximately $139.3 million in principal balances of finance receivables under the 2017 Master Transfer Agreement. During the year ended December 31, 2018, the Company sold approximately $348.8 million in principal balances of finance receivables under the 2017 Master Transfer Agreement, and approximately $115.0 million in principal balances of finance receivables under the 2018 Transfer Agreement, excluding those that were part of the refinancing transactions described below.

During the year ended December 31, 2019, prior to the certificate purchase, the Company also purchased finance receivables that it previously sold to the purchaser trust under the 2017 Master Transfer Agreement for a total price of approximately $127.7 million and immediately resold such finance receivables into a securitization transaction, which is described further in Note 8 — Securitizations and Variable Interest Entities. This transaction was entered into in connection with the securitization transaction and was entered into independently from the terms of the 2017 Master Transfer Agreement.

The total gain related to finance receivables sold to financing partners under the MPSA, the 2016 Master Transfer Agreement, the 2017 Master Transfer Agreement, and to investors in securitization transactions discussed in Note 8 — Securitizations and Variable Interest Entities was approximately $137.3 million, $51.7 million, and $21.7 million during the years ended December 31, 2019, 2018, and 2017, respectively, which is included in other sales and revenues in the accompanying consolidated statements of operations.