Variable Interest Entities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Subordinated Borrowing [Line Items]
Federal tax credits recognized in tax expense	$ 660	$ 520	$ 1,990	$ 1,550
Investment tax credits	570	$ 0	25,020	$ 9,480
Investment carrying amount	8,525,058		8,525,058		$ 8,339,416
Unfunded capital and other commitments	7,542,061		7,542,061		7,415,650
Maximum exposure to loss, unconsolidated VIEs	65,643		65,643		45,020
Variable Interest Entity [Line Items]
Investment carrying amount	8,525,058		8,525,058		8,339,416
Variable interest entity, primary beneficiary
Subordinated Borrowing [Line Items]
Investment carrying amount	65,180		65,180		66,260
Unfunded capital and other commitments	0		0		0
Variable Interest Entity [Line Items]
Investment carrying amount	65,180		65,180		66,260
Variable interest entity, not primary beneficiary
Subordinated Borrowing [Line Items]
Investment carrying amount	84,818		84,818		70,887
Unfunded capital and other commitments	76,505		76,505		64,520
Variable Interest Entity [Line Items]
Investment carrying amount	$ 84,818		$ 84,818		$ 70,887