Fair Value Measurements - Fair Value by Hierarchy (Details) - USD ($)	3 Months Ended		4 Months Ended	5 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	May 31, 2018	Sep. 30, 2017	Jun. 01, 2018	Dec. 31, 2017
Fair Value Measurement [Domain]
Assets, Fair Value Disclosure [Abstract]
Separate Account Assets	$ 103,673,000,000		$ 103,673,000,000				$ 113,302,000,000
Fair value assets level 2 to level 1 transfer amount	0	$ 0	0	$ 0	$ 0
Debt Securities, Available-for-sale	14,072,000,000		14,072,000,000				22,799,000,000
Fair Value, Option, Fixed Maturity Securities	14,000,000		14,000,000				32,000,000
Trading Securities, Equity							12,000,000
Equity Securities, FV-NI	109,000,000		109,000,000
Available-for-sale Securities, Equity Securities	0		0				154,000,000
Derivative Asset							135,000,000
Other Short-term Investments	1,159,000,000		1,159,000,000				1,094,000,000
Reinsurance Recoverables, Including Reinsurance Premium Paid	29,819,000,000		29,819,000,000			$ 22,615,000,000	20,785,000,000
Separate Account Assets	106,829,000,000		106,829,000,000			$ 110,773,000,000	115,834,000,000
Assets, Fair Value Disclosure	119,130,000,000		119,130,000,000				137,619,000,000
Liabilities, Fair Value Disclosure [Abstract]
Financial and Nonfinancial Liabilities, Fair Value Disclosure	563,000,000		563,000,000				663,000,000
Portion at Other than Fair Value Measurement [Member]
Assets, Fair Value Disclosure [Abstract]
Separate Account Assets	2,700,000,000		2,700,000,000				2,500,000,000
Estimate of Fair Value Measurement [Member]
Assets, Fair Value Disclosure [Abstract]
Separate Account Assets	500,000,000		500,000,000				900,000,000
Liability [Member]
Liabilities, Fair Value Disclosure [Abstract]
Obligations, Fair Value Disclosure	(12,000,000)		(12,000,000)				(75,000,000)
Guaranteed Minimum Withdrawal Benefit [Member]
Liabilities, Fair Value Disclosure [Abstract]
Obligations, Fair Value Disclosure	(12,000,000)		(12,000,000)				(75,000,000)
Credit Risk Contract [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	3,000,000		3,000,000				1,000,000
Interest Rate Contract [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	(2,000,000)		(2,000,000)				47,000,000
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	290,000,000		290,000,000				403,000,000
US GMWB Hedging Instruments [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	28,000,000		28,000,000				69,000,000
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	(12,000,000)		(12,000,000)				(2,000,000)
Macro Hedge Program [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	47,000,000		47,000,000				19,000,000
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	(85,000,000)		(85,000,000)				4,000,000
Derivative Financial Instruments, Assets [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	76,000,000		76,000,000
GMWB Reinsurance [Member]
Assets, Fair Value Disclosure [Abstract]
Reinsurance Recoverables, Including Reinsurance Premium Paid	17,000,000		17,000,000				36,000,000
Coinsurance and Modified Coinsurance Reinsurance Contracts [Member]
Assets, Fair Value Disclosure [Abstract]
Reinsurance Recoverable, Including Reinsurance Premium Paid MODCO	10,000,000		10,000,000				55,000,000
Foreign Exchange Contract [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset							(1,000,000)
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	190,000,000		190,000,000				187,000,000
Derivative Financial Instruments, Liabilities [Member]
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	(575,000,000)		(575,000,000)				(588,000,000)
ABS [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	558,000,000		558,000,000				819,000,000
CDOs
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	769,000,000		769,000,000				888,000,000
CMBS [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	1,398,000,000		1,398,000,000				2,084,000,000
Corporate
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	7,910,000,000		7,910,000,000				14,038,000,000
Debt Security, Government, Non-US [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	371,000,000		371,000,000				407,000,000
US States and Political Subdivisions Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	723,000,000		723,000,000				1,266,000,000
RMBS [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	1,030,000,000		1,030,000,000				1,427,000,000
Fair Value, Option, Fixed Maturity Securities	14,000,000		14,000,000				32,000,000
U.S. Treasuries
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	1,313,000,000		1,313,000,000				1,870,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value Measurement [Domain]
Assets, Fair Value Disclosure [Abstract]
Separate Account Assets	68,704,000,000		68,704,000,000
Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	101,000,000		101,000,000				284,000,000
Fair Value, Option, Fixed Maturity Securities	0		0				0
Trading Securities, Equity							12,000,000
Equity Securities, FV-NI	47,000,000		47,000,000
Available-for-sale Securities, Equity Securities							61,000,000
Other Short-term Investments	469,000,000		469,000,000				807,000,000
Separate Account Assets							73,538,000,000
Assets, Fair Value Disclosure	69,321,000,000		69,321,000,000				74,702,000,000
Liabilities, Fair Value Disclosure [Abstract]
Financial and Nonfinancial Liabilities, Fair Value Disclosure	0		0				0
Fair Value, Inputs, Level 1 [Member] | Liability [Member]
Liabilities, Fair Value Disclosure [Abstract]
Obligations, Fair Value Disclosure	0		0				0
Fair Value, Inputs, Level 1 [Member] | Guaranteed Minimum Withdrawal Benefit [Member]
Liabilities, Fair Value Disclosure [Abstract]
Obligations, Fair Value Disclosure	0		0				0
Fair Value, Inputs, Level 1 [Member] | Credit Risk Contract [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	0		0				0
Fair Value, Inputs, Level 1 [Member] | Interest Rate Contract [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	0		0				0
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	0		0				0
Fair Value, Inputs, Level 1 [Member] | US GMWB Hedging Instruments [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	0		0				0
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	0		0				0
Fair Value, Inputs, Level 1 [Member] | Macro Hedge Program [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	0		0				0
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	0		0				0
Fair Value, Inputs, Level 1 [Member] | GMWB Reinsurance [Member]
Assets, Fair Value Disclosure [Abstract]
Reinsurance Recoverables, Including Reinsurance Premium Paid	0		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				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				0
Fair Value, Inputs, Level 1 [Member] | Derivative Financial Instruments, Liabilities [Member]
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	0		0				0
Fair Value, Inputs, Level 1 [Member] | ABS [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	0		0				0
Fair Value, Inputs, Level 1 [Member] | CDOs
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	0		0				0
Fair Value, Inputs, Level 1 [Member] | CMBS [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	0		0				0
Fair Value, Inputs, Level 1 [Member] | Corporate
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	0		0				0
Fair Value, Inputs, Level 1 [Member] | Debt Security, Government, Non-US [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	0		0				0
Fair Value, Inputs, Level 1 [Member] | US States and Political Subdivisions Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	0		0				0
Fair Value, Inputs, Level 1 [Member] | RMBS [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	0		0				0
Fair Value, Inputs, Level 1 [Member] | U.S. Treasuries
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	101,000,000		101,000,000				284,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value Measurement [Domain]
Assets, Fair Value Disclosure [Abstract]
Separate Account Assets	34,912,000,000		34,912,000,000
Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	12,951,000,000		12,951,000,000				21,229,000,000
Fair Value, Option, Fixed Maturity Securities	14,000,000		14,000,000				32,000,000
Trading Securities, Equity							0
Equity Securities, FV-NI	19,000,000		19,000,000
Available-for-sale Securities, Equity Securities							47,000,000
Derivative Asset							82,000,000
Other Short-term Investments	690,000,000		690,000,000				287,000,000
Separate Account Assets							38,677,000,000
Assets, Fair Value Disclosure	48,602,000,000		48,602,000,000				60,409,000,000
Liabilities, Fair Value Disclosure [Abstract]
Financial and Nonfinancial Liabilities, Fair Value Disclosure	444,000,000		444,000,000				563,000,000
Fair Value, Inputs, Level 2 [Member] | Liability [Member]
Liabilities, Fair Value Disclosure [Abstract]
Obligations, Fair Value Disclosure	0		0				0
Fair Value, Inputs, Level 2 [Member] | Guaranteed Minimum Withdrawal Benefit [Member]
Liabilities, Fair Value Disclosure [Abstract]
Obligations, Fair Value Disclosure	0		0				0
Fair Value, Inputs, Level 2 [Member] | Credit Risk Contract [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	3,000,000		3,000,000				1,000,000
Fair Value, Inputs, Level 2 [Member] | Interest Rate Contract [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	(2,000,000)		(2,000,000)				47,000,000
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	264,000,000		264,000,000				374,000,000
Fair Value, Inputs, Level 2 [Member] | US GMWB Hedging Instruments [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	5,000,000		5,000,000				35,000,000
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	8,000,000		8,000,000				(2,000,000)
Fair Value, Inputs, Level 2 [Member] | Macro Hedge Program [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	0		0				0
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	0		0				0
Fair Value, Inputs, Level 2 [Member] | Derivative Financial Instruments, Assets [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	6,000,000		6,000,000
Fair Value, Inputs, Level 2 [Member] | GMWB Reinsurance [Member]
Assets, Fair Value Disclosure [Abstract]
Reinsurance Recoverables, Including Reinsurance Premium Paid	0		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	10,000,000		10,000,000				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	190,000,000		190,000,000				187,000,000
Fair Value, Inputs, Level 2 [Member] | Derivative Financial Instruments, Liabilities [Member]
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	(444,000,000)		(444,000,000)				(563,000,000)
Fair Value, Inputs, Level 2 [Member] | ABS [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	540,000,000		540,000,000				806,000,000
Fair Value, Inputs, Level 2 [Member] | CDOs
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	610,000,000		610,000,000				815,000,000
Fair Value, Inputs, Level 2 [Member] | CMBS [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	1,395,000,000		1,395,000,000				2,058,000,000
Fair Value, Inputs, Level 2 [Member] | Corporate
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	7,553,000,000		7,553,000,000				13,595,000,000
Fair Value, Inputs, Level 2 [Member] | Debt Security, Government, Non-US [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	371,000,000		371,000,000				406,000,000
Fair Value, Inputs, Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	711,000,000		711,000,000				1,228,000,000
Fair Value, Inputs, Level 2 [Member] | RMBS [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	559,000,000		559,000,000				735,000,000
Fair Value, Inputs, Level 2 [Member] | U.S. Treasuries
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	1,212,000,000		1,212,000,000				1,586,000,000
Fair Value, Inputs, Level 3 [Member] | Fair Value Measurement [Domain]
Assets, Fair Value Disclosure [Abstract]
Separate Account Assets	57,000,000		57,000,000
Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	1,020,000,000		1,020,000,000				1,286,000,000
Fair Value, Option, Fixed Maturity Securities	0		0				0
Trading Securities, Equity							0
Equity Securities, FV-NI	43,000,000		43,000,000
Available-for-sale Securities, Equity Securities							46,000,000
Derivative Asset							53,000,000
Other Short-term Investments	0		0				0
Separate Account Assets							185,000,000
Assets, Fair Value Disclosure	1,207,000,000		1,207,000,000				1,606,000,000
Liabilities, Fair Value Disclosure [Abstract]
Financial and Nonfinancial Liabilities, Fair Value Disclosure	119,000,000		119,000,000				100,000,000
Fair Value, Inputs, Level 3 [Member] | Liability [Member]
Liabilities, Fair Value Disclosure [Abstract]
Obligations, Fair Value Disclosure	(12,000,000)		(12,000,000)				(75,000,000)
Fair Value, Inputs, Level 3 [Member] | Guaranteed Minimum Withdrawal Benefit [Member]
Liabilities, Fair Value Disclosure [Abstract]
Obligations, Fair Value Disclosure	(12,000,000)		(12,000,000)				(75,000,000)
Fair Value, Inputs, Level 3 [Member] | Credit Risk Contract [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	0		0				0
Fair Value, Inputs, Level 3 [Member] | Interest Rate Contract [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	0		0				0
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	26,000,000		26,000,000				29,000,000
Fair Value, Inputs, Level 3 [Member] | US GMWB Hedging Instruments [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	23,000,000		23,000,000				34,000,000
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	(20,000,000)		(20,000,000)				0
Fair Value, Inputs, Level 3 [Member] | Macro Hedge Program [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	47,000,000		47,000,000				19,000,000
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	(85,000,000)		(85,000,000)				4,000,000
Fair Value, Inputs, Level 3 [Member] | Derivative Financial Instruments, Assets [Member]
Assets, Fair Value Disclosure [Abstract]
Derivative Asset	70,000,000		70,000,000
Fair Value, Inputs, Level 3 [Member] | GMWB Reinsurance [Member]
Assets, Fair Value Disclosure [Abstract]
Reinsurance Recoverables, Including Reinsurance Premium Paid	17,000,000		17,000,000				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				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				0
Fair Value, Inputs, Level 3 [Member] | Derivative Financial Instruments, Liabilities [Member]
Liabilities, Fair Value Disclosure [Abstract]
Derivative Liability	(131,000,000)		(131,000,000)				(25,000,000)
Fair Value, Inputs, Level 3 [Member] | ABS [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	18,000,000		18,000,000				13,000,000
Fair Value, Inputs, Level 3 [Member] | CDOs
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	159,000,000		159,000,000				73,000,000
Fair Value, Inputs, Level 3 [Member] | CMBS [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	3,000,000		3,000,000				26,000,000
Fair Value, Inputs, Level 3 [Member] | Corporate
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	357,000,000		357,000,000				443,000,000
Fair Value, Inputs, Level 3 [Member] | Debt Security, Government, Non-US [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	0		0				1,000,000
Fair Value, Inputs, Level 3 [Member] | US States and Political Subdivisions Debt Securities [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	12,000,000		12,000,000				38,000,000
Fair Value, Inputs, Level 3 [Member] | RMBS [Member]
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	471,000,000		471,000,000				692,000,000
Fair Value, Inputs, Level 3 [Member] | U.S. Treasuries
Assets, Fair Value Disclosure [Abstract]
Debt Securities, Available-for-sale	0		0				$ 0
Other Liabilities [Member] | Credit Risk Contract [Member]
Liabilities, Fair Value Disclosure [Abstract]
Derivative Assets (Liabilities), at Fair Value, Net	2,000,000		2,000,000
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		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	2,000,000		2,000,000
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		$ 0