Premiums Receivable and Other Insurance Assets Premiums Receivable and Other Insurance Assets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Premiums and Other Receivables, Net [Abstract]
Prepaid reinsurance premiums	$ 551	$ 527
Reinsurance recoverables on unpaid losses	88	96
Reinsurance recoverables on paid losses	23	22
Premiums receivable	105	88
Deferred policy acquisition cost	1,791	1,593
Premiums receivable and other insurance assets	$ 2,558	$ 2,326