Acquisition (Details) - USD ($) $ in Millions		3 Months Ended
	Jan. 03, 2017	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill		$ 2,189		$ 2,181
SquareTrade
Business Acquisition [Line Items]
Consideration transferred	$ 1,400
Goodwill	1,100
Commissions paid to retailers	66
Intangible assets	555
Prepaid contractual liability insurance policy premium expenses	205
Unearned premiums	389
Net deferred income tax liability	138
Amortization of intangible assets		$ 21	$ 23
Customer Relationships | SquareTrade
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	465
Trade Names | SquareTrade
Business Acquisition [Line Items]
Indefinite-lived intangible assets acquired	$ 69