Insurance (Rollfoward of Unpaid Claims) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Liability for Claims and Claims Adjustment Expense [Line Items]
Balance at January 1,	$ 11,388	$ 11,036	$ 10,630
Less: Reinsurance recoverables	2,042	1,876	1,661
Net balance at January 1,	14,334	9,160	8,969
Incurred related to:
Current year	25,085	9,639	9,358
Prior years	369	(78)	(70)
Total incurred	25,454	9,561	9,288
Paid related to:
Current year	(17,356)	(6,788)	(6,714)
Prior years	(7,331)	(2,587)	(2,383)
Total paid	(24,687)	(9,375)	(9,097)
Net balance at December 31,	15,101	14,334	9,160
Add: Reinsurance recoverables	3,058	2,042	1,876
Balance at December 31,	18,159	11,388	11,036
Scenario, Previously Reported
Liability for Claims and Claims Adjustment Expense [Line Items]
Net balance at January 1,	9,346	9,160	8,969
Paid related to:
Net balance at December 31,		9,346	9,160
Cumulative adjustment
Liability for Claims and Claims Adjustment Expense [Line Items]
Net balance at January 1,	$ 4,988	0	0
Paid related to:
Net balance at December 31,		$ 4,988	$ 0