Fair Value Measurements - Investments - Schedule of Quantitative Information (Details) $ in Thousands	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Infrastructure Assets	$ 1,021,161	$ 983,552
Level III
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Infrastructure Assets	$ 1,021,161	$ 983,552
Weighted Average | Level III | Illiquidity Discount
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, measurement input	0.051	0.051
Weighted Average | Level III | Weight Ascribed to Market Comparables
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, measurement input	0.038	0.040
Weighted Average | Level III | Weight Ascribed to Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, measurement input	0.945	0.946
Weighted Average | Level III | Weight Ascribed to Transaction Price/Other
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, measurement input	0.017	0.014
Weighted Average | Level III | Enterprise Value / Forward EBITDA Multiple | Market Comparables
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, measurement input	10.6	10.5
Weighted Average | Level III | Weighted Average Cost of Capital | Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, measurement input	0.098	0.097
Weighted Average | Level III | Enterprise Value / LTM EBITDA Exit Multiple | Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, measurement input	13.8	13.9
Minimum | Level III | Illiquidity Discount
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, measurement input	0.050	0.050
Minimum | Level III | Weight Ascribed to Market Comparables
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, measurement input	0	0
Minimum | Level III | Weight Ascribed to Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, measurement input	0	0
Minimum | Level III | Weight Ascribed to Transaction Price/Other
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, measurement input	0	0
Minimum | Level III | Enterprise Value / Forward EBITDA Multiple | Market Comparables
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, measurement input	10.6	10.5
Minimum | Level III | Weighted Average Cost of Capital | Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, measurement input	0.069	0.067
Minimum | Level III | Enterprise Value / LTM EBITDA Exit Multiple | Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, measurement input	7.1	9.5
Maximum | Level III | Illiquidity Discount
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, measurement input	0.100	0.100
Maximum | Level III | Weight Ascribed to Market Comparables
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, measurement input	0.250	0.250
Maximum | Level III | Weight Ascribed to Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, measurement input	1.000	1.000
Maximum | Level III | Weight Ascribed to Transaction Price/Other
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, measurement input	1.000	1.000
Maximum | Level III | Enterprise Value / Forward EBITDA Multiple | Market Comparables
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, measurement input	10.6	10.5
Maximum | Level III | Weighted Average Cost of Capital | Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, measurement input	0.149	0.121
Maximum | Level III | Enterprise Value / LTM EBITDA Exit Multiple | Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Investments, measurement input	20.0	21.0