Insurance (Rollforward of Unpaid Claims) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Liability for Claims and Claims Adjustment Expense [Line Items]
Balance at beginning of period	$ 18,159	$ 11,388
Less: Reinsurance recoverables	3,058	2,042
Net Balance, beginning of period	15,101	14,334
Incurred related to:
Current period	13,126	12,985
Prior years	14	28
Total incurred	13,140	13,013
Paid related to:
Current period	(8,850)	(8,351)
Prior periods	(3,811)	(3,772)
Total paid	(12,661)	(12,123)
Net Balance, end of period	15,580	15,224
Add: Reinsurance recoverables	3,182	2,873
Balance at end of period (included in future policy benefits and other policy-related balances)	18,762	18,097
Scenario, Previously Reported
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Balance, beginning of period	15,101	9,346
Cumulative adjustment
Liability for Claims and Claims Adjustment Expense [Line Items]
Net Balance, beginning of period	$ 0	$ 4,988