3. Securitization Trust Debt (Details) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2018	Dec. 31, 2017
"Securitization trust debt," and components of debt
Receivables Pledged at end of period	[1]	$ 2,114,248
Initial Principal		4,742,413
Outstanding Principal		$ 2,042,682	$ 2,095,675
CPS 2013-B [Member]
"Securitization trust debt," and components of debt
Final Scheduled Payment Date	[2]	September 2020
Receivables Pledged at end of period	[1]	$ 0
Initial Principal		205,000
Outstanding Principal		$ 0	18,407
Weighted Average Contractual Interest Rate		0.00%
CPS 2013-C [Member]
"Securitization trust debt," and components of debt
Final Scheduled Payment Date	[2]	December 2020
Receivables Pledged at end of period	[1]	$ 0
Initial Principal		205,000
Outstanding Principal		$ 0	25,559
Weighted Average Contractual Interest Rate		0.00%
CPS 2013-D [Member]
"Securitization trust debt," and components of debt
Final Scheduled Payment Date	[2]	March 2021
Receivables Pledged at end of period	[1]	$ 19,366
Initial Principal		183,000
Outstanding Principal		$ 17,737	24,917
Weighted Average Contractual Interest Rate		5.57%
CPS 2014-A [Member]
"Securitization trust debt," and components of debt
Final Scheduled Payment Date	[2]	June 2021
Receivables Pledged at end of period	[1]	$ 24,224
Initial Principal		180,000
Outstanding Principal		$ 21,894	30,521
Weighted Average Contractual Interest Rate		4.74%
CPS 2014-B [Member]
"Securitization trust debt," and components of debt
Final Scheduled Payment Date	[2]	September 2021
Receivables Pledged at end of period	[1]	$ 35,335
Initial Principal		202,500
Outstanding Principal		$ 33,419	44,516
Weighted Average Contractual Interest Rate		4.09%
CPS 2014-C [Member]
"Securitization trust debt," and components of debt
Final Scheduled Payment Date	[2]	December 2021
Receivables Pledged at end of period	[1]	$ 56,842
Initial Principal		273,000
Outstanding Principal		$ 55,081	71,174
Weighted Average Contractual Interest Rate		4.22%
CPS 2014-D [Member]
"Securitization trust debt," and components of debt
Final Scheduled Payment Date	[2]	March 2022
Receivables Pledged at end of period	[1]	$ 63,322
Initial Principal		267,500
Outstanding Principal		$ 61,433	79,099
Weighted Average Contractual Interest Rate		4.52%
CPS 2015-A [Member]
"Securitization trust debt," and components of debt
Final Scheduled Payment Date	[2]	June 2022
Receivables Pledged at end of period	[1]	$ 70,365
Initial Principal		245,000
Outstanding Principal		$ 68,531	87,194
Weighted Average Contractual Interest Rate		4.09%
CPS 2015-B [Member]
"Securitization trust debt," and components of debt
Final Scheduled Payment Date	[2]	September 2022
Receivables Pledged at end of period	[1]	$ 83,535
Initial Principal		250,000
Outstanding Principal		$ 82,450	102,873
Weighted Average Contractual Interest Rate		4.11%
CPS 2015-C [Member]
"Securitization trust debt," and components of debt
Final Scheduled Payment Date	[2]	December 2022
Receivables Pledged at end of period	[1]	$ 115,839
Initial Principal		300,000
Outstanding Principal		$ 114,701	141,362
Weighted Average Contractual Interest Rate		4.52%
CPS 2016-A [Member]
"Securitization trust debt," and components of debt
Final Scheduled Payment Date	[2]	March 2023
Receivables Pledged at end of period	[1]	$ 150,370
Initial Principal		329,460
Outstanding Principal		$ 148,789	180,761
Weighted Average Contractual Interest Rate		4.82%
CPS 2016-B [Member]
"Securitization trust debt," and components of debt
Final Scheduled Payment Date	[2]	June 2023
Receivables Pledged at end of period	[1]	$ 170,132
Initial Principal		332,690
Outstanding Principal		$ 166,163	201,199
Weighted Average Contractual Interest Rate		4.99%
CPS 2016-C [Member]
"Securitization trust debt," and components of debt
Final Scheduled Payment Date	[2]	September 2023
Receivables Pledged at end of period	[1]	$ 172,255
Initial Principal		318,500
Outstanding Principal		$ 168,262	203,504
Weighted Average Contractual Interest Rate		4.57%
CPS 2016-D [Member]
"Securitization trust debt," and components of debt
Final Scheduled Payment Date	[2]	April 2024
Receivables Pledged at end of period	[1]	$ 128,194
Initial Principal		206,325
Outstanding Principal		$ 125,394	149,671
Weighted Average Contractual Interest Rate		3.46%
CPS 2017-A [Member]
"Securitization trust debt," and components of debt
Final Scheduled Payment Date	[2]	April 2024
Receivables Pledged at end of period	[1]	$ 139,256
Initial Principal		206,320
Outstanding Principal		$ 135,994	161,892
Weighted Average Contractual Interest Rate		3.62%
CPS 2017-B [Member]
"Securitization trust debt," and components of debt
Final Scheduled Payment Date	[2]	December 2023
Receivables Pledged at end of period	[1]	$ 167,524
Initial Principal		225,170
Outstanding Principal		$ 155,525	186,594
Weighted Average Contractual Interest Rate		3.13%
CPS 2017-C [Member]
"Securitization trust debt," and components of debt
Final Scheduled Payment Date	[2]	September 2024
Receivables Pledged at end of period	[1]	$ 172,642
Initial Principal		224,825
Outstanding Principal		$ 163,372	197,155
Weighted Average Contractual Interest Rate		3.05%
CPS 2017-D [Member]
"Securitization trust debt," and components of debt
Final Scheduled Payment Date	[2]	June 2024
Receivables Pledged at end of period	[1]	$ 169,697
Initial Principal		196,300
Outstanding Principal		$ 160,527	189,277
Weighted Average Contractual Interest Rate		2.90%
CPS 2018-A [Member]
"Securitization trust debt," and components of debt
Final Scheduled Payment Date	[2]	March 2025
Receivables Pledged at end of period	[1]	$ 176,804
Initial Principal		190,000
Outstanding Principal		$ 168,757	0
Weighted Average Contractual Interest Rate		2.98%
CPS 2018-B [Member]
"Securitization trust debt," and components of debt
Final Scheduled Payment Date	[2]	December 2024
Receivables Pledged at end of period	[1]	$ 198,546
Initial Principal		201,823
Outstanding Principal		$ 194,653	$ 0
Weighted Average Contractual Interest Rate		3.46%

[1] Includes repossessed assets that are included in Other assets on our Unaudited Condensed Consolidated Balance Sheet.

[2] The Final Scheduled Payment Date represents final legal maturity of the securitization trust debt. Securitization trust debt is expected to become due and to be paid prior to those dates, based on amortization of the finance receivables pledged to the trusts. Expected payments, which will depend on the performance of such receivables, as to which there can be no assurance, are $468.4 million in 2018, $760.0 million in 2019, $458.5 million in 2020, $234.5 million in 2021, $90.4 million in 2022, $18.9 million in 2023.