Fair Value Measurements - Fair Value by Hierarchy (Details) - USD ($)	1 Months Ended	2 Months Ended	3 Months Ended	5 Months Ended	6 Months Ended
	Jun. 30, 2018	May 31, 2018	Jun. 30, 2017	May 31, 2018	Jun. 30, 2017	Jun. 01, 2018	Dec. 31, 2017
Fair Value Measurement [Domain]
Assets, Fair Value Disclosure [Abstract]
Separate Account Assets	$ 104,488,000,000						$ 113,302,000,000
Fair value assets level 2 to level 1 transfer amount	0	$ 0	$ 0	$ 0	$ 0
Available-for-sale Securities, Debt Securities	14,409,000,000						22,799,000,000
Fair Value, Option, Fixed Maturity Securities	18,000,000						32,000,000
Trading Securities, Equity							12,000,000
Marketable Securities, Equity Securities	131,000,000
Available-for-sale Securities, Equity Securities	0						154,000,000
Derivative Asset							135,000,000
Other Short-term Investments	939,000,000						1,094,000,000
Reinsurance Recoverables, Including Reinsurance Premium Paid	30,132,000,000					$ 22,615,000,000	20,785,000,000
Separate Account Assets	109,595,000,000					$ 110,773,000,000	115,834,000,000
Assets, Fair Value Disclosure	120,054,000,000						137,619,000,000
Liabilities, Fair Value Disclosure [Abstract]
Financial and Nonfinancial Liabilities, Fair Value Disclosure	509,000,000						663,000,000
Portion at Other than Fair Value Measurement [Member]
Assets, Fair Value Disclosure [Abstract]
Separate Account Assets	4,600,000,000						2,500,000,000
Estimate of Fair Value Measurement [Member]
Assets, Fair Value Disclosure [Abstract]
Separate Account Assets	502,000,000						900,000,000
Liability [Member]
Liabilities, Fair Value Disclosure [Abstract]
Obligations, Fair Value Disclosure	(18,000,000)						(75,000,000)
Guaranteed Minimum Withdrawal Benefit [Member]
Liabilities, Fair Value Disclosure [Abstract]
Obligations, Fair Value Disclosure	(18,000,000)						(75,000,000)
Credit Risk Contract [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	4,000,000						1,000,000
Interest Rate Contract [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	(2,000,000)						47,000,000
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	318,000,000						403,000,000
US GMWB Hedging Instruments [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	29,000,000						69,000,000
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	11,000,000						(2,000,000)
Macro Hedge Program [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	9,000,000						19,000,000
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	(6,000,000)						4,000,000
Derivative Financial Instruments, Assets [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	40,000,000
GMWB Reinsurance [Member]
Assets, Fair Value Disclosure [Abstract]
Reinsurance Recoverables, Including Reinsurance Premium Paid	22,000,000						36,000,000
Coinsurance and Modified Coinsurance Reinsurance Contracts [Member]
Assets, Fair Value Disclosure [Abstract]
Reinsurance Recoverable, Including Reinsurance Premium Paid MODCO	7,000,000						55,000,000
Foreign Exchange Contract [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset							(1,000,000)
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	179,000,000						187,000,000
Derivative Financial Instruments, Liabilities [Member]
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	(491,000,000)						(588,000,000)
ABS [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	540,000,000						819,000,000
CDOs
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	699,000,000						888,000,000
CMBS [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	1,423,000,000						2,084,000,000
Corporate
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	8,211,000,000						14,038,000,000
Foreign Government Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	374,000,000						407,000,000
US States and Political Subdivisions Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	776,000,000						1,266,000,000
RMBS [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	1,058,000,000						1,427,000,000
U.S. Treasuries
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	1,328,000,000						1,870,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value Measurement [Domain]
Assets, Fair Value Disclosure [Abstract]
Separate Account Assets	68,452,000,000
Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	13,000,000						284,000,000
Fair Value, Option, Fixed Maturity Securities	0						0
Trading Securities, Equity							12,000,000
Marketable Securities, Equity Securities	46,000,000
Available-for-sale Securities, Equity Securities							61,000,000
Other Short-term Investments	454,000,000						807,000,000
Separate Account Assets							73,538,000,000
Assets, Fair Value Disclosure	68,965,000,000						74,702,000,000
Liabilities, Fair Value Disclosure [Abstract]
Financial and Nonfinancial Liabilities, Fair Value Disclosure	0						0
Fair Value, Inputs, Level 1 [Member] | Liability [Member]
Liabilities, Fair Value Disclosure [Abstract]
Obligations, Fair Value Disclosure	0						0
Fair Value, Inputs, Level 1 [Member] | Guaranteed Minimum Withdrawal Benefit [Member]
Liabilities, Fair Value Disclosure [Abstract]
Obligations, Fair Value Disclosure	0						0
Fair Value, Inputs, Level 1 [Member] | Credit Risk Contract [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	0						0
Fair Value, Inputs, Level 1 [Member] | Interest Rate Contract [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	0						0
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	0						0
Fair Value, Inputs, Level 1 [Member] | US GMWB Hedging Instruments [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	0						0
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	0						0
Fair Value, Inputs, Level 1 [Member] | Macro Hedge Program [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	0						0
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	0						0
Fair Value, Inputs, Level 1 [Member] | GMWB Reinsurance [Member]
Assets, Fair Value Disclosure [Abstract]
Reinsurance Recoverables, Including Reinsurance Premium Paid	0						0
Fair Value, Inputs, Level 1 [Member] | Coinsurance and Modified Coinsurance Reinsurance Contracts [Member]
Assets, Fair Value Disclosure [Abstract]
Reinsurance Recoverable, Including Reinsurance Premium Paid MODCO	0						0
Fair Value, Inputs, Level 1 [Member] | Foreign Exchange Contract [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset							0
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	0						0
Fair Value, Inputs, Level 1 [Member] | Derivative Financial Instruments, Liabilities [Member]
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	0						0
Fair Value, Inputs, Level 1 [Member] | ABS [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	0						0
Fair Value, Inputs, Level 1 [Member] | CDOs
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	0						0
Fair Value, Inputs, Level 1 [Member] | CMBS [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	0						0
Fair Value, Inputs, Level 1 [Member] | Corporate
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	0						0
Fair Value, Inputs, Level 1 [Member] | Foreign Government Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	0						0
Fair Value, Inputs, Level 1 [Member] | US States and Political Subdivisions Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	0						0
Fair Value, Inputs, Level 1 [Member] | RMBS [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	0						0
Fair Value, Inputs, Level 1 [Member] | U.S. Treasuries
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	13,000,000						284,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value Measurement [Domain]
Assets, Fair Value Disclosure [Abstract]
Separate Account Assets	35,962,000,000
Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	13,332,000,000						21,229,000,000
Fair Value, Option, Fixed Maturity Securities	18,000,000						32,000,000
Trading Securities, Equity							0
Marketable Securities, Equity Securities	42,000,000
Available-for-sale Securities, Equity Securities							47,000,000
Derivative Asset							82,000,000
Other Short-term Investments	485,000,000						287,000,000
Separate Account Assets							38,677,000,000
Assets, Fair Value Disclosure	49,848,000,000						60,409,000,000
Liabilities, Fair Value Disclosure [Abstract]
Financial and Nonfinancial Liabilities, Fair Value Disclosure	446,000,000						563,000,000
Fair Value, Inputs, Level 2 [Member] | Liability [Member]
Liabilities, Fair Value Disclosure [Abstract]
Obligations, Fair Value Disclosure	0						0
Fair Value, Inputs, Level 2 [Member] | Guaranteed Minimum Withdrawal Benefit [Member]
Liabilities, Fair Value Disclosure [Abstract]
Obligations, Fair Value Disclosure	0						0
Fair Value, Inputs, Level 2 [Member] | Credit Risk Contract [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	4,000,000						1,000,000
Fair Value, Inputs, Level 2 [Member] | Interest Rate Contract [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	(2,000,000)						47,000,000
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	291,000,000						374,000,000
Fair Value, Inputs, Level 2 [Member] | US GMWB Hedging Instruments [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	0						35,000,000
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	23,000,000						(2,000,000)
Fair Value, Inputs, Level 2 [Member] | Macro Hedge Program [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	0						0
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	0						0
Fair Value, Inputs, Level 2 [Member] | Derivative Financial Instruments, Assets [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	2,000,000
Fair Value, Inputs, Level 2 [Member] | GMWB Reinsurance [Member]
Assets, Fair Value Disclosure [Abstract]
Reinsurance Recoverables, Including Reinsurance Premium Paid	0						0
Fair Value, Inputs, Level 2 [Member] | Coinsurance and Modified Coinsurance Reinsurance Contracts [Member]
Assets, Fair Value Disclosure [Abstract]
Reinsurance Recoverable, Including Reinsurance Premium Paid MODCO	7,000,000						55,000,000
Fair Value, Inputs, Level 2 [Member] | Foreign Exchange Contract [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset							(1,000,000)
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	179,000,000						187,000,000
Fair Value, Inputs, Level 2 [Member] | Derivative Financial Instruments, Liabilities [Member]
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	(446,000,000)						(563,000,000)
Fair Value, Inputs, Level 2 [Member] | ABS [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	520,000,000						806,000,000
Fair Value, Inputs, Level 2 [Member] | CDOs
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	604,000,000						815,000,000
Fair Value, Inputs, Level 2 [Member] | CMBS [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	1,416,000,000						2,058,000,000
Fair Value, Inputs, Level 2 [Member] | Corporate
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	7,815,000,000						13,595,000,000
Fair Value, Inputs, Level 2 [Member] | Foreign Government Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	374,000,000						406,000,000
Fair Value, Inputs, Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	764,000,000						1,228,000,000
Fair Value, Inputs, Level 2 [Member] | RMBS [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	524,000,000						735,000,000
Fair Value, Inputs, Level 2 [Member] | U.S. Treasuries
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	1,315,000,000						1,586,000,000
Fair Value, Inputs, Level 3 [Member] | Fair Value Measurement [Domain]
Assets, Fair Value Disclosure [Abstract]
Separate Account Assets	74,000,000
Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	1,064,000,000						1,286,000,000
Fair Value, Option, Fixed Maturity Securities	0						0
Trading Securities, Equity							0
Marketable Securities, Equity Securities	43,000,000
Available-for-sale Securities, Equity Securities							46,000,000
Derivative Asset							53,000,000
Other Short-term Investments	0						0
Separate Account Assets							185,000,000
Assets, Fair Value Disclosure	1,241,000,000						1,606,000,000
Liabilities, Fair Value Disclosure [Abstract]
Financial and Nonfinancial Liabilities, Fair Value Disclosure	63,000,000						100,000,000
Fair Value, Inputs, Level 3 [Member] | Liability [Member]
Liabilities, Fair Value Disclosure [Abstract]
Obligations, Fair Value Disclosure	(18,000,000)						(75,000,000)
Fair Value, Inputs, Level 3 [Member] | Guaranteed Minimum Withdrawal Benefit [Member]
Liabilities, Fair Value Disclosure [Abstract]
Obligations, Fair Value Disclosure	(18,000,000)						(75,000,000)
Fair Value, Inputs, Level 3 [Member] | Credit Risk Contract [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	0						0
Fair Value, Inputs, Level 3 [Member] | Interest Rate Contract [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	0						0
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	27,000,000						29,000,000
Fair Value, Inputs, Level 3 [Member] | US GMWB Hedging Instruments [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	29,000,000						34,000,000
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	(12,000,000)						0
Fair Value, Inputs, Level 3 [Member] | Macro Hedge Program [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	9,000,000						19,000,000
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	(6,000,000)						4,000,000
Fair Value, Inputs, Level 3 [Member] | Derivative Financial Instruments, Assets [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	38,000,000
Fair Value, Inputs, Level 3 [Member] | GMWB Reinsurance [Member]
Assets, Fair Value Disclosure [Abstract]
Reinsurance Recoverables, Including Reinsurance Premium Paid	22,000,000						36,000,000
Fair Value, Inputs, Level 3 [Member] | Coinsurance and Modified Coinsurance Reinsurance Contracts [Member]
Assets, Fair Value Disclosure [Abstract]
Reinsurance Recoverable, Including Reinsurance Premium Paid MODCO	0						0
Fair Value, Inputs, Level 3 [Member] | Foreign Exchange Contract [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset							0
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	0						0
Fair Value, Inputs, Level 3 [Member] | Derivative Financial Instruments, Liabilities [Member]
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	(45,000,000)						(25,000,000)
Fair Value, Inputs, Level 3 [Member] | ABS [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	20,000,000						13,000,000
Fair Value, Inputs, Level 3 [Member] | CDOs
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	95,000,000						73,000,000
Fair Value, Inputs, Level 3 [Member] | CMBS [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	7,000,000						26,000,000
Fair Value, Inputs, Level 3 [Member] | Corporate
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	396,000,000						443,000,000
Fair Value, Inputs, Level 3 [Member] | Foreign Government Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	0						1,000,000
Fair Value, Inputs, Level 3 [Member] | US States and Political Subdivisions Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	12,000,000						38,000,000
Fair Value, Inputs, Level 3 [Member] | RMBS [Member]
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	534,000,000						692,000,000
Fair Value, Inputs, Level 3 [Member] | U.S. Treasuries
Assets, Fair Value Disclosure [Abstract]
Available-for-sale Securities, Debt Securities	0						$ 0
Other Liabilities [Member] | Credit Risk Contract [Member]
Liabilities, Fair Value Disclosure [Abstract]
Derivative Assets (Liabilities), at Fair Value, Net	1,000,000
Other Liabilities [Member] | Fair Value, Inputs, Level 1 [Member] | Credit Risk Contract [Member]
Liabilities, Fair Value Disclosure [Abstract]
Derivative Assets (Liabilities), at Fair Value, Net	0
Other Liabilities [Member] | Fair Value, Inputs, Level 2 [Member] | Credit Risk Contract [Member]
Liabilities, Fair Value Disclosure [Abstract]
Derivative Assets (Liabilities), at Fair Value, Net	1,000,000
Other Liabilities [Member] | Fair Value, Inputs, Level 3 [Member] | Credit Risk Contract [Member]
Liabilities, Fair Value Disclosure [Abstract]
Derivative Assets (Liabilities), at Fair Value, Net	$ 0