Debt - Schedule of Senior Securities (Including Debt Securities and Other Indebtedness) (Details) - Senior Notes - USD ($) $ / shares in Units, $ in Thousands	Mar. 31, 2026	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
8.25% Notes due 2020
Debt Instrument [Line Items]
Total Amount Outstanding											$ 33,646
Asset Coverage Ratio Per Unit											$ 6,168
Average Market Value Per Unit											$ 1.02
GECCL Notes
Debt Instrument [Line Items]
Total Amount Outstanding							$ 30,293	$ 32,631	$ 32,631	$ 32,631
Asset Coverage Ratio Per Unit							$ 1,671	$ 1,701	$ 2,393	$ 5,010
Average Market Value Per Unit							$ 0.89	$ 1.01	$ 1.01	$ 1.02
GECCM Notes
Debt Instrument [Line Items]
Total Amount Outstanding				$ 45,610	$ 45,610	$ 45,610	$ 45,610	$ 46,398	$ 46,398
Asset Coverage Ratio Per Unit				$ 1,690	$ 1,544	$ 1,511	$ 1,671	$ 1,701	$ 2,393
Average Market Value Per Unit				$ 0.99	$ 0.99	$ 1	$ 0.84	$ 1.01	$ 0.98
GECCN Notes
Debt Instrument [Line Items]
Total Amount Outstanding					$ 42,823	$ 42,823	$ 42,823	$ 45,000
Asset Coverage Ratio Per Unit					$ 1,544	$ 1,511	$ 1,671	$ 1,701
Average Market Value Per Unit					$ 1	$ 1	$ 0.84	$ 1
GECCO Notes
Debt Instrument [Line Items]
Total Amount Outstanding	$ 18,628	$ 38,983	$ 57,500	$ 57,500	$ 57,500	$ 57,500
Asset Coverage Ratio Per Unit	$ 1,618	$ 1,581	$ 1,697	$ 1,690	$ 1,544	$ 1,511
Average Market Value Per Unit	$ 1	$ 1.01	$ 0.99	$ 0.96	$ 1	$ 1.02
GECCZ Notes
Debt Instrument [Line Items]
Total Amount Outstanding			$ 40,000	$ 40,000
Asset Coverage Ratio Per Unit			$ 1,697	$ 1,690
Average Market Value Per Unit			$ 1.01	$ 0.99
GECCI Notes
Debt Instrument [Line Items]
Total Amount Outstanding	$ 56,500	$ 56,500	$ 56,500
Asset Coverage Ratio Per Unit	$ 1,618	$ 1,581	$ 1,697
Average Market Value Per Unit	$ 1.01	$ 1.01	$ 1.01
GECCH Notes
Debt Instrument [Line Items]
Total Amount Outstanding	$ 41,400	$ 41,400	$ 41,400
Asset Coverage Ratio Per Unit	$ 1,618	$ 1,581	$ 1,697
Average Market Value Per Unit	$ 1.01	$ 1	$ 1
GECCG Notes
Debt Instrument [Line Items]
Total Amount Outstanding	$ 57,500	$ 57,500
Asset Coverage Ratio Per Unit	$ 1,618	$ 1,581
Average Market Value Per Unit	$ 0.99	$ 1
Revolving Credit Facility
Debt Instrument [Line Items]
Total Amount Outstanding					$ 10,000
Asset Coverage Ratio Per Unit	$ 1,618	$ 1,581	$ 1,697	$ 1,690	$ 1,544