Geographic Regions (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Revenues and Pretax Income (Loss) by Geographic Location [Line Items]
Revenues	$ 377	$ 388	$ 418	$ 432	$ 406	$ 386	$ 351	$ 318	$ 1,615	$ 1,461	$ 1,087
Pretax income	$ 132	$ 131	$ 130	$ 119	$ 108	$ 107	$ 93	$ 108	512	416	275
United States [Member]
Segment Revenues and Pretax Income (Loss) by Geographic Location [Line Items]
Revenues									1,133	1,033	779
Pretax income									61	28	9
Outside the United States [Member]
Segment Revenues and Pretax Income (Loss) by Geographic Location [Line Items]
Revenues									482	428	308
Pretax income									$ 451	$ 388	$ 266