| Segment Reporting [Table Text Block] |
| Three Months Ended June 30, 2026 | | CaaS | | | Auto Finance | | | Total | |
| Revenue and other income: | | | | | | | | | | | | |
| Consumer loans, including past due fees | | $ | 535,507 | | | $ | 9,579 | | | $ | 545,086 | |
| Fees and related income on earning assets | | | 150,548 | | | | 330 | | | | 150,878 | |
| Other revenue | | | 48,147 | | | | 203 | | | | 48,350 | |
| Total operating revenue and other income | | | 734,202 | | | | 10,112 | | | | 744,314 | |
| Other non-operating income | | | 9 | | | | — | | | | 9 | |
| Total revenue and other income | | | 734,211 | | | | 10,112 | | | | 744,323 | |
| Interest expense | | | (123,082 | ) | | | (349 | ) | | | (123,431 | ) |
| Provision for credit losses | | | (386 | ) | | | (652 | ) | | | (1,038 | ) |
| Changes in fair value of loans | | | (396,280 | ) | | | — | | | | (396,280 | ) |
| Net margin | | | 214,463 | | | | 9,111 | | | | 223,574 | |
| Operating expenses: | | | | | | | | | | | | |
| Salaries and benefits | | | (25,978 | ) | | | (1,272 | ) | | | (27,250 | ) |
| Card and loan servicing | | | (54,408 | ) | | | (3,455 | ) | | | (57,863 | ) |
| Marketing and solicitation | | | (48,047 | ) | | | (83 | ) | | | (48,130 | ) |
| Depreciation and amortization | | | (3,573 | ) | | | (19 | ) | | | (3,592 | ) |
| Other | | | (19,477 | ) | | | (1,255 | ) | | | (20,732 | ) |
| Total operating expenses | | | (151,483 | ) | | | (6,084 | ) | | | (157,567 | ) |
| Income before income taxes | | $ | 62,980 | | | $ | 3,027 | | | $ | 66,007 | |
| Six Months Ended June 30, 2026 | | CaaS | | | Auto Finance | | | Total | |
| Revenue and other income: | | | | | | | | | | | | |
| Consumer loans, including past due fees | | $ | 1,055,409 | | | $ | 19,122 | | | $ | 1,074,531 | |
| Fees and related income on earning assets | | | 260,637 | | | | 670 | | | | 261,307 | |
| Other revenue | | | 87,594 | | | | 416 | | | | 88,010 | |
| Total operating revenue and other income | | | 1,403,640 | | | | 20,208 | | | | 1,423,848 | |
| Other non-operating income | | | 64 | | | | — | | | | 64 | |
| Total revenue and other income | | | 1,403,704 | | | | 20,208 | | | | 1,423,912 | |
| Interest expense | | | (245,475 | ) | | | (717 | ) | | | (246,192 | ) |
| Provision for credit losses | | | (1,196 | ) | | | (1,442 | ) | | | (2,638 | ) |
| Changes in fair value of loans | | | (761,804 | ) | | | — | | | | (761,804 | ) |
| Net margin | | | 395,229 | | | | 18,049 | | | | 413,278 | |
| Operating expenses: | | | | | | | | | | | | |
| Salaries and benefits | | | (53,440 | ) | | | (2,456 | ) | | | (55,896 | ) |
| Card and loan servicing | | | (95,905 | ) | | | (6,876 | ) | | | (102,781 | ) |
| Marketing and solicitation | | | (84,504 | ) | | | (99 | ) | | | (84,603 | ) |
| Depreciation and amortization | | | (7,141 | ) | | | (37 | ) | | | (7,178 | ) |
| Other | | | (35,597 | ) | | | (2,368 | ) | | | (37,965 | ) |
| Total operating expenses | | | (276,587 | ) | | | (11,836 | ) | | | (288,423 | ) |
| Income before income taxes | | $ | 118,642 | | | $ | 6,213 | | | $ | 124,855 | |
| Total assets | | $ | 7,408,285 | | | $ | 83,485 | | | $ | 7,491,770 | |
| Three Months Ended June 30, 2025 | | CaaS | | | Auto Finance | | | Total | |
| Revenue and other income: | | | | | | | | | | | | |
| Consumer loans, including past due fees | | $ | 267,204 | | | $ | 9,146 | | | $ | 276,350 | |
| Fees and related income on earning assets | | | 94,262 | | | | 23 | | | | 94,285 | |
| Other revenue | | | 23,012 | | | | 173 | | | | 23,185 | |
| Total operating revenue and other income | | | 384,478 | | | | 9,342 | | | | 393,820 | |
| Other non-operating income | | | 6 | | | | 337 | | | | 343 | |
| Total revenue and other income | | | 384,484 | | | | 9,679 | | | | 394,163 | |
| Interest expense | | | (53,162 | ) | | | (522 | ) | | | (53,684 | ) |
| Provision for credit losses | | | (189 | ) | | | (1,193 | ) | | | (1,382 | ) |
| Changes in fair value of loans | | | (216,777 | ) | | | — | | | | (216,777 | ) |
| Net margin | | | 114,356 | | | | 7,964 | | | | 122,320 | |
| Operating expenses: | | | | | | | | | | | | |
| Salaries and benefits | | | (12,133 | ) | | | (1,248 | ) | | | (13,381 | ) |
| Card and loan servicing | | | (30,764 | ) | | | (3,321 | ) | | | (34,085 | ) |
| Marketing and solicitation | | | (24,912 | ) | | | (37 | ) | | | (24,949 | ) |
| Depreciation and amortization | | | (866 | ) | | | (19 | ) | | | (885 | ) |
| Other | | | (7,685 | ) | | | (1,189 | ) | | | (8,874 | ) |
| Total operating expenses | | | (76,360 | ) | | | (5,814 | ) | | | (82,174 | ) |
| Income (loss) before income taxes | | $ | 37,996 | | | $ | 2,150 | | | $ | 40,146 | |
| Six Months Ended June 30, 2025 | | CaaS | | | Auto Finance | | | Total | |
| Revenue and other income: | | | | | | | | | | | | |
| Consumer loans, including past due fees | | $ | 505,707 | | | $ | 18,298 | | | $ | 524,005 | |
| Fees and related income on earning assets | | | 172,585 | | | | 41 | | | | 172,626 | |
| Other revenue | | | 41,710 | | | | 352 | | | | 42,062 | |
| Total operating revenue and other income | | | 720,002 | | | | 18,691 | | | | 738,693 | |
| Other non-operating income | | | 13 | | | | 623 | | | | 636 | |
| Total revenue and other income | | | 720,015 | | | | 19,314 | | | | 739,329 | |
| Interest expense | | | (100,146 | ) | | | (1,068 | ) | | | (101,214 | ) |
| Provision for credit losses | | | (214 | ) | | | (2,236 | ) | | | (2,450 | ) |
| Changes in fair value of loans | | | (395,122 | ) | | | — | | | | (395,122 | ) |
| Net margin | | | 224,533 | | | | 16,010 | | | | 240,543 | |
| Operating expenses: | | | | | | | | | | | | |
| Salaries and benefits | | | (26,419 | ) | | | (2,465 | ) | | | (28,884 | ) |
| Card and loan servicing | | | (59,621 | ) | | | (6,616 | ) | | | (66,237 | ) |
| Marketing and solicitation | | | (45,239 | ) | | | (44 | ) | | | (45,283 | ) |
| Depreciation and amortization | | | (1,644 | ) | | | (38 | ) | | | (1,682 | ) |
| Other | | | (15,219 | ) | | | (2,224 | ) | | | (17,443 | ) |
| Total operating expenses | | | (148,142 | ) | | | (11,387 | ) | | | (159,529 | ) |
| Income before income taxes | | $ | 76,391 | | | $ | 4,623 | | | $ | 81,014 | |
| Total assets | | $ | 3,555,841 | | | $ | 87,334 | | | $ | 3,643,175 | |
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