Derivatives (Effects on the Consolidated Statement of Operations and Comprehensive Income (Loss)) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ 115,000,000	$ 349,000,000
Net Investment Income	4,908,000,000	3,745,000,000
Gain (Loss) on Investments	15,000,000	(333,000,000)
Policyholder Benefits and Claims Incurred, Net	9,072,000,000	8,718,000,000
Interest Credited to Policyholders Account Balances	1,961,000,000	769,000,000
Operating Expenses	3,225,000,000	3,365,000,000
Nonperformance Risk [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Embedded Derivative, Gain (Loss) on Embedded Derivative, Net	(62,000,000)	20,000,000
Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	3,000,000
Net Investment Income	(1,000,000)	0
Gain (Loss) on Investments	(18,000,000)	0
Policyholder Benefits and Claims Incurred, Net	(1,000,000)	0
Interest Credited to Policyholders Account Balances	0	0
Operating Expenses	0	0
Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	22,000,000
Net Investment Income	3,000,000	4,000,000
Gain (Loss) on Investments	(15,000,000)	0
Interest Credited to Policyholders Account Balances	0	0
Operating Expenses	1,000,000	1,000,000
Other Comprehensive Income (Loss), before Tax	(13,000,000)	(517,000,000)
Net Investment Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), before Tax	(6,000,000)	(157,000,000)
Foreign Exchange Forward [Member] | Net Investment Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), before Tax		(157,000,000)
Interest Rate Contract | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	21,000,000
Net Investment Income	5,000,000	4,000,000
Gain (Loss) on Investments	(6,000,000)	0
Policyholder Benefits and Claims Incurred, Net	0	0
Interest Credited to Policyholders Account Balances	0	0
Operating Expenses	1,000,000	0
Other Comprehensive Income (Loss), before Tax	0	(25,000,000)
Designated as Hedging Instrument [Member] | Net Investment Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), before Tax	(6,000,000)
Credit forwards [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	0
Net Investment Income	0	0
Gain (Loss) on Investments	1,000,000	0
Policyholder Benefits and Claims Incurred, Net	0	0
Interest Credited to Policyholders Account Balances	0	0
Operating Expenses	0	0
Other Comprehensive Income (Loss), before Tax	(1,000,000)	0
Currency Swap [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	139,000,000
Net Investment Income	(2,000,000)	0
Gain (Loss) on Investments	25,000,000	0
Policyholder Benefits and Claims Incurred, Net	0	0
Interest Credited to Policyholders Account Balances	0	0
Operating Expenses	0	1,000,000
Other Comprehensive Income (Loss), before Tax	(23,000,000)	(140,000,000)
Derivative [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	(8,000,000)
Net Investment Income	0	0
Gain (Loss) on Investments	(16,000,000)	0
Policyholder Benefits and Claims Incurred, Net	0	0
Interest Credited to Policyholders Account Balances	0	0
Operating Expenses	0	0
Derivative [Member] | Interest rate swaps | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	(210,000,000)
Net Investment Income	(3,000,000)	0
Gain (Loss) on Investments	0	0
Policyholder Benefits and Claims Incurred, Net	127,000,000	0
Interest Credited to Policyholders Account Balances	0	0
Operating Expenses	0	0
Derivative [Member] | Currency Swap [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	170,000,000
Net Investment Income	(30,000,000)	0
Gain (Loss) on Investments	(14,000,000)	0
Policyholder Benefits and Claims Incurred, Net	0	0
Interest Credited to Policyholders Account Balances	0	0
Operating Expenses	0	0
Debt Securities | Interest rate swaps | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	210,000,000
Net Investment Income	3,000,000	0
Gain (Loss) on Investments	0	0
Policyholder Benefits and Claims Incurred, Net	(128,000,000)	0
Interest Credited to Policyholders Account Balances	0	0
Operating Expenses	0	0
Debt Securities | Currency Swap [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	(159,000,000)
Net Investment Income	29,000,000	0
Gain (Loss) on Investments	12,000,000	0
Policyholder Benefits and Claims Incurred, Net	0	0
Interest Credited to Policyholders Account Balances	0	0
Operating Expenses	0	0
Foreign Currency Gain (Loss) [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0	(138,000,000)
Net Investment Income	0	0
Gain (Loss) on Investments	(35,000,000)	0
Policyholder Benefits and Claims Incurred, Net	0	0
Interest Credited to Policyholders Account Balances	0	0
Operating Expenses	0	0
Other Comprehensive Income (Loss), before Tax	0	0
Accumulated Other Comprehensive Income (Loss) | Credit forwards [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), before Tax	0	0
Accumulated Other Comprehensive Income (Loss) | Currency Swap [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), before Tax	(241,000,000)	(75,000,000)
Accumulated Other Comprehensive Income (Loss) | Interest rate swaps | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), before Tax	252,000,000	(277,000,000)
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(197,000,000)	154,000,000
Net Investment Income	(1,000,000)	5,000,000
Gain (Loss) on Investments	0	0
Policyholder Benefits and Claims Incurred, Net	(74,000,000)	7,000,000
Interest Credited to Policyholders Account Balances	0	0
Operating Expenses	0	0
Foreign Exchange [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(142,000,000)	387,000,000
Net Investment Income	0	0
Gain (Loss) on Investments	0	0
Policyholder Benefits and Claims Incurred, Net	3,000,000	2,000,000
Interest Credited to Policyholders Account Balances	0	0
Operating Expenses	0	0
Credit derivatives — purchased | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(15,000,000)	(3,000,000)
Net Investment Income	0	0
Gain (Loss) on Investments	0	0
Policyholder Benefits and Claims Incurred, Net	0	0
Interest Credited to Policyholders Account Balances	0	0
Operating Expenses	0	0
Credit derivatives — written | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	136,000,000	(44,000,000)
Net Investment Income	0	0
Gain (Loss) on Investments	0	0
Policyholder Benefits and Claims Incurred, Net	0	0
Interest Credited to Policyholders Account Balances	0	0
Operating Expenses	0	0
Equity Market Risk [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(667,000,000)	98,000,000
Net Investment Income	0	1,000,000
Gain (Loss) on Investments	0	0
Policyholder Benefits and Claims Incurred, Net	(96,000,000)	12,000,000
Interest Credited to Policyholders Account Balances	0	0
Operating Expenses	0	0
Foreign Currency Gain (Loss) [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	82,000,000	(49,000,000)
Net Investment Income	0	0
Gain (Loss) on Investments	0	0
Policyholder Benefits and Claims Incurred, Net	0	0
Interest Credited to Policyholders Account Balances	0	0
Operating Expenses	0	0
Interest Rate Risk [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	409,000,000	(235,000,000)
Net Investment Income	(1,000,000)	4,000,000
Gain (Loss) on Investments	0	0
Policyholder Benefits and Claims Incurred, Net	19,000,000	(7,000,000)
Interest Credited to Policyholders Account Balances	0	0
Operating Expenses	0	0
Net Derivative Gain (Loss) [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	119,000,000	133,000,000
Net Investment Income	56,000,000	81,000,000
Gain (Loss) on Investments	0	0
Policyholder Benefits and Claims Incurred, Net	32,000,000	2,000,000
Interest Credited to Policyholders Account Balances	(32,000,000)	(23,000,000)
Operating Expenses	0	(2,000,000)
Other Comprehensive Income (Loss), before Tax	0	0
Embedded Derivative Financial Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	193,000,000	37,000,000
Policyholder Benefits and Claims Incurred, Net	0	0
Effects of Derivatives on Consolidated Statements of Operations and Comprehensive Income (Loss) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net Investment Income	57,000,000	90,000,000
Gain (Loss) on Investments	(33,000,000)	0
Policyholder Benefits and Claims Incurred, Net	(43,000,000)	9,000,000
Interest Credited to Policyholders Account Balances	(32,000,000)	(23,000,000)
Operating Expenses	1,000,000	(1,000,000)
Other Comprehensive Income (Loss), before Tax	$ (19,000,000)	$ (674,000,000)