Variable Interest Entities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Subordinated notes
Federal tax credits recognized in tax expense	$ 2,660	$ 2,060	$ 2,020
Investment tax credits	37,230	9,830	$ 3,530
Investment carrying amount	8,727,958	8,339,416
Unfunded capital and other commitments	7,659,695	7,415,650
Unconsolidated maximum exposure to loss	59,649	45,020
Variable interest entity, primary beneficiary
Subordinated notes
Investment carrying amount	87,370	66,260
Unfunded capital and other commitments	0	0
Variable interest entity, not primary beneficiary
Subordinated notes
Investment carrying amount	79,228	70,887
Unfunded capital and other commitments	$ 80,719	$ 64,520