Insurance Premiums and Service Revenue Insurance Premiums and Service Revenue (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Insurance Premiums and Service Revenue [Abstract]
Direct premiums written	$ 491	$ 420	$ 384
Direct premiums earned	464	414	364
Assumed premiums written	0	0	2
Assumed premiums earned	2	4	5
Premiums written, gross	491	420	386
Premiums earned, gross	466	418	369
Ceded premiums written	(232)	(219)	(254)
Ceded premiums earned	(209)	(197)	(188)
Premiums written, net	259	201	132
Premiums earned, net	257	221	181
Service revenue written	1,051	973	864
Service revenue earned	830	801	792
Insurance premiums and service revenue written	1,310	1,174	996
Insurance premiums and service revenue earned	$ 1,087	$ 1,022	$ 973