Acquisitions and Dispositions - Intangible asset by type (Details) - National General Holdings Corp. - USD ($) $ in Millions		6 Months Ended
	Jan. 04, 2021	Jun. 30, 2021
Business Acquisition [Line Items]
Intangible assets	$ 1,199
Maximum
Business Acquisition [Line Items]
Finite-lived intangible asset, useful life (in years)	10 years	12 months
Minimum
Business Acquisition [Line Items]
Finite-lived intangible asset, useful life (in years)	3 years	6 months
Distribution and customer relationships
Business Acquisition [Line Items]
Intangible assets	$ 795
Trade names
Business Acquisition [Line Items]
Intangible assets	102
Licenses
Business Acquisition [Line Items]
Intangible assets	97
Technology
Business Acquisition [Line Items]
Intangible assets	$ 205