Segment Information - Summarized Financial Information Reportable Segments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Segment Reporting Information [Line Items]
Total revenues	$ 1,178	$ 1,047	$ 2,435	$ 2,163
Investment income	22	10	40	17
Amortization	44	41	86	83
Depreciation	11	10	21	20
Interest expense	49	48	97	95
Income before income taxes	346	254	712	548
Total assets	15,944	14,072	15,944	14,072	$ 14,883
Capital expenditures	27	13	39	25
Operating Segments | Retail
Segment Reporting Information [Line Items]
Total revenues	646	591	1,452	1,324
Investment income	1	0	2	0
Amortization	29	28	58	56
Depreciation	5	5	10	10
Interest expense	19	22	38	44
Income before income taxes	129	106	367	320
Total assets	8,676	8,192	8,676	8,192
Capital expenditures	20	9	27	15
Operating Segments | Programs
Segment Reporting Information [Line Items]
Total revenues	359	310	657	565
Investment income	5	2	10	3
Amortization	12	11	23	22
Depreciation	4	3	8	6
Interest expense	7	9	16	19
Income before income taxes	183	124	285	199
Total assets	4,723	3,997	4,723	3,997
Capital expenditures	6	3	10	8
Operating Segments | Wholesale Brokerage
Segment Reporting Information [Line Items]
Total revenues	159	139	301	262
Investment income	1	0	2	0
Amortization	3	3	6	6
Depreciation	1	1	2	2
Interest expense	3	3	6	6
Income before income taxes	47	38	88	69
Total assets	1,659	1,423	1,659	1,423
Capital expenditures	1	1	1	1
Segment Reconciling Items
Segment Reporting Information [Line Items]
Total revenues	14	7	25	12
Investment income	15	8	26	14
Amortization	0	(1)	(1)	(1)
Depreciation	1	1	1	2
Interest expense	20	14	37	26
Income before income taxes	(13)	(14)	(28)	(40)
Total assets	886	460	886	460
Capital expenditures	$ 0	$ 0	$ 1	$ 1