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Fair Value Measurements - Summary of Changes in Fair Value of Investments Measured Using Level 3 Inputs (Details) - USD ($) $ in Thousands | 3 Months Ended |  |
--- | --- | --- | ---
Mar. 31, 2023 | Mar. 31, 2022 | Dec. 31, 2022 | Dec. 31, 2021
Total Investments |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Fair value, beginning of period | $ 9,426,489 | $ 9,760,202 | $ 9,472,796 | $ 9,501,329
Purchases of investments | 114,640 | 260,839 |  |
Proceeds from principal repayments and sales of investments | (71,040) | (45,718) |  |
Accretion of discount/amortization of premium | 8,443 | 9,231 |  |
Transfers into Level 3 | 4,938 | 25,772 |  |
Transfers out of Level 3 | (91,939) | 0 |  |
Fair value, end of period | 9,426,489 | 9,760,202 |  |
Net change in unrealized appreciation (depreciation) included in earnings related to financial instruments, included in net unrealized appreciation (depreciation) on the Consolidated Statements of Operations | (11,395) | 7,251 |  |
Investments, Realized Gain (Loss) |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Net realized gain (loss) | 46 | 5,858 |  |
Investments, Unrealized Gain (Loss) |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Net realized gain (loss) | (11,395) | 2,891 |  |
First lien debt |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Fair value, beginning of period | 9,225,290 | 9,541,813 | 9,275,511 | 9,288,184
Purchases of investments | 114,229 | 253,310 |  |
Proceeds from principal repayments and sales of investments | (71,040) | (35,031) |  |
Accretion of discount/amortization of premium | 8,407 | 9,212 |  |
Transfers into Level 3 | 4,938 | 25,772 |  |
Transfers out of Level 3 | (91,939) | 0 |  |
Fair value, end of period | 9,225,290 | 9,541,813 |  |
Net change in unrealized appreciation (depreciation) included in earnings related to financial instruments, included in net unrealized appreciation (depreciation) on the Consolidated Statements of Operations | (14,862) | 18 |  |
Debt Securities, First Lien, Realized Gain (Loss) |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Net realized gain (loss) | 46 | (62) |  |
Debt Securities, First Lien, Unrealized Gain (Loss) |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Net realized gain (loss) | (14,862) | 428 |  |
Second lien debt |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Fair value, beginning of period | 46,678 | 43,243 | 46,336 | 42,880
Purchases of investments | 411 | 265 |  |
Proceeds from principal repayments and sales of investments | 0 | 0 |  |
Accretion of discount/amortization of premium | 36 | 19 |  |
Transfers into Level 3 | 0 | 0 |  |
Transfers out of Level 3 | 0 | 0 |  |
Fair value, end of period | 46,678 | 43,243 |  |
Net change in unrealized appreciation (depreciation) included in earnings related to financial instruments, included in net unrealized appreciation (depreciation) on the Consolidated Statements of Operations | (105) | 81 |  |
Debt Securities, Second Lien, Realized Gain (Loss) |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Net realized gain (loss) | 0 | 0 |  |
Debt Securities, Second Lien, Unrealized Gain (Loss) |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Net realized gain (loss) | (105) | 79 |  |
Investments in equity |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Fair value, beginning of period | 154,521 | 175,146 | $ 150,949 | $ 170,265
Purchases of investments | 0 | 7,264 |  |
Proceeds from principal repayments and sales of investments | 0 | (10,687) |  |
Accretion of discount/amortization of premium | 0 | 0 |  |
Transfers into Level 3 | 0 | 0 |  |
Transfers out of Level 3 | 0 | 0 |  |
Fair value, end of period | 154,521 | 175,146 |  |
Net change in unrealized appreciation (depreciation) included in earnings related to financial instruments, included in net unrealized appreciation (depreciation) on the Consolidated Statements of Operations | 3,572 | 7,152 |  |
Equity Securities, Realized Gain (Loss) |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Net realized gain (loss) | 0 | 5,920 |  |
Equity Securities, Unrealized Gain (Loss) |  |  |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Net realized gain (loss) | $ 3,572 | $ 2,384 |  |

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