Fair Value of Financial Instruments (Fair Value Inputs Quantitative Information) (Details) - Significant Unobservable Inputs (Level 3) [Member] - Discounted Cash Flow Valuation Technique [Member]	Mar. 31, 2019 USD ($)
Corporate Bonds [Member] | Fixed Maturity Securities [Member]
Assets Fair Value Disclosure [Abstract]
Assets Fair Value Disclosure	$ 2,604,000,000
Corporate Bonds [Member] | Maximum [Member] | Fixed Maturity Securities [Member] | Liquidity/Duration Adjustment [Member]
Liabilities Fair Value Disclosure [Abstract]
Fixed maturity AFS and trading securities, measurement input	0.300
Corporate Bonds [Member] | Minimum [Member] | Fixed Maturity Securities [Member] | Liquidity/Duration Adjustment [Member]
Liabilities Fair Value Disclosure [Abstract]
Fixed maturity AFS and trading securities, measurement input	0.006
ABS [Member] | Fixed Maturity Securities [Member]
Assets Fair Value Disclosure [Abstract]
Assets Fair Value Disclosure	$ 23,000,000
ABS [Member] | Maximum [Member] | Fixed Maturity Securities [Member] | Liquidity/Duration Adjustment [Member]
Liabilities Fair Value Disclosure [Abstract]
Fixed maturity AFS and trading securities, measurement input	0.030
ABS [Member] | Minimum [Member] | Fixed Maturity Securities [Member] | Liquidity/Duration Adjustment [Member]
Liabilities Fair Value Disclosure [Abstract]
Fixed maturity AFS and trading securities, measurement input	0.030
Foreign Government Bonds [Member] | Fixed Maturity Securities [Member]
Assets Fair Value Disclosure [Abstract]
Assets Fair Value Disclosure	$ 77,000,000
Foreign Government Bonds [Member] | Maximum [Member] | Fixed Maturity Securities [Member] | Liquidity/Duration Adjustment [Member]
Liabilities Fair Value Disclosure [Abstract]
Fixed maturity AFS and trading securities, measurement input	0.031
Foreign Government Bonds [Member] | Minimum [Member] | Fixed Maturity Securities [Member] | Liquidity/Duration Adjustment [Member]
Liabilities Fair Value Disclosure [Abstract]
Fixed maturity AFS and trading securities, measurement input	0.014
Hybrid And Redeemable Preferred Securities [Member] | Fixed Maturity Securities [Member]
Assets Fair Value Disclosure [Abstract]
Assets Fair Value Disclosure	$ 4,000,000
Hybrid And Redeemable Preferred Securities [Member] | Maximum [Member] | Fixed Maturity Securities [Member] | Liquidity/Duration Adjustment [Member]
Liabilities Fair Value Disclosure [Abstract]
Fixed maturity AFS and trading securities, measurement input	0.016
Hybrid And Redeemable Preferred Securities [Member] | Minimum [Member] | Fixed Maturity Securities [Member] | Liquidity/Duration Adjustment [Member]
Liabilities Fair Value Disclosure [Abstract]
Fixed maturity AFS and trading securities, measurement input	0.016
Equity Securities [Member] | Fixed Maturity Securities [Member]
Assets Fair Value Disclosure [Abstract]
Assets Fair Value Disclosure	$ 21,000,000
Equity Securities [Member] | Maximum [Member] | Fixed Maturity Securities [Member] | Liquidity/Duration Adjustment [Member]
Liabilities Fair Value Disclosure [Abstract]
Equity securities, measurement input	0.052
Equity Securities [Member] | Minimum [Member] | Fixed Maturity Securities [Member] | Liquidity/Duration Adjustment [Member]
Liabilities Fair Value Disclosure [Abstract]
Equity securities, measurement input	0.045
GLB Direct And Ceded Embedded Derivative [Member] | Other Assets [Member]
Assets Fair Value Disclosure [Abstract]
Assets Fair Value Disclosure	$ 489,000,000
GLB Direct And Ceded Embedded Derivative [Member] | Maximum [Member] | Other Assets [Member] | Lapse Rate [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative assets, measurement input	0.30
GLB Direct And Ceded Embedded Derivative [Member] | Maximum [Member] | Other Assets [Member] | Utilization Of Guaranteed Withdrawls [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative assets, measurement input	1.00
GLB Direct And Ceded Embedded Derivative [Member] | Maximum [Member] | Other Assets [Member] | Claims Utilization Factor [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative assets, measurement input	1.00
GLB Direct And Ceded Embedded Derivative [Member] | Maximum [Member] | Other Assets [Member] | Premiums Utilization Factor [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative assets, measurement input	1.15
GLB Direct And Ceded Embedded Derivative [Member] | Maximum [Member] | Other Assets [Member] | NPR [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative assets, measurement input	0.0032
GLB Direct And Ceded Embedded Derivative [Member] | Maximum [Member] | Other Assets [Member] | Volatility [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative assets, measurement input	0.29
GLB Direct And Ceded Embedded Derivative [Member] | Minimum [Member] | Other Assets [Member] | Lapse Rate [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative assets, measurement input	0.01
GLB Direct And Ceded Embedded Derivative [Member] | Minimum [Member] | Other Assets [Member] | Utilization Of Guaranteed Withdrawls [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative assets, measurement input	0.85
GLB Direct And Ceded Embedded Derivative [Member] | Minimum [Member] | Other Assets [Member] | Claims Utilization Factor [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative assets, measurement input	0.60
GLB Direct And Ceded Embedded Derivative [Member] | Minimum [Member] | Other Assets [Member] | Premiums Utilization Factor [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative assets, measurement input	0.80
GLB Direct And Ceded Embedded Derivative [Member] | Minimum [Member] | Other Assets [Member] | NPR [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative assets, measurement input	0.0002
GLB Direct And Ceded Embedded Derivative [Member] | Minimum [Member] | Other Assets [Member] | Volatility [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative assets, measurement input	0.01
Indexed Annuity And IUL Contracts [Member] | Other Assets [Member]
Assets Fair Value Disclosure [Abstract]
Assets Fair Value Disclosure	$ 872,000,000
Indexed Annuity And IUL Contracts [Member] | Maximum [Member] | Other Assets [Member] | Lapse Rate [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative assets, measurement input	0.09
Indexed Annuity And IUL Contracts [Member] | Minimum [Member] | Other Assets [Member] | Lapse Rate [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative assets, measurement input	0.01
Future contract benefits - indexed annuity and IUL contracts embedded derivatives | Future Contract Benefits [Member]
Liabilities Fair Value Disclosure [Abstract]
Liabilities measured at fair value	$ (1,730,000,000)
Future contract benefits - indexed annuity and IUL contracts embedded derivatives | Maximum [Member] | Future Contract Benefits [Member] | Lapse Rate [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative liability, measurement input	0.09
Future contract benefits - indexed annuity and IUL contracts embedded derivatives | Minimum [Member] | Future Contract Benefits [Member] | Lapse Rate [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative liability, measurement input	0.01
GLB Ceded Embedded Derivatives [Member] | Other Liabilities [Member]
Liabilities Fair Value Disclosure [Abstract]
Liabilities measured at fair value	$ (489,000,000)
GLB Ceded Embedded Derivatives [Member] | Maximum [Member] | Other Liabilities [Member] | Lapse Rate [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative liability, measurement input	0.30
GLB Ceded Embedded Derivatives [Member] | Maximum [Member] | Other Liabilities [Member] | Utilization Of Guaranteed Withdrawls [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative liability, measurement input	1.00
GLB Ceded Embedded Derivatives [Member] | Maximum [Member] | Other Liabilities [Member] | Claims Utilization Factor [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative liability, measurement input	1.00
GLB Ceded Embedded Derivatives [Member] | Maximum [Member] | Other Liabilities [Member] | Premiums Utilization Factor [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative liability, measurement input	1.15
GLB Ceded Embedded Derivatives [Member] | Maximum [Member] | Other Liabilities [Member] | NPR [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative liability, measurement input	0.0032
GLB Ceded Embedded Derivatives [Member] | Maximum [Member] | Other Liabilities [Member] | Volatility [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative liability, measurement input	0.29
GLB Ceded Embedded Derivatives [Member] | Minimum [Member] | Other Liabilities [Member] | Lapse Rate [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative liability, measurement input	0.01
GLB Ceded Embedded Derivatives [Member] | Minimum [Member] | Other Liabilities [Member] | Utilization Of Guaranteed Withdrawls [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative liability, measurement input	0.85
GLB Ceded Embedded Derivatives [Member] | Minimum [Member] | Other Liabilities [Member] | Claims Utilization Factor [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative liability, measurement input	0.60
GLB Ceded Embedded Derivatives [Member] | Minimum [Member] | Other Liabilities [Member] | Premiums Utilization Factor [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative liability, measurement input	0.80
GLB Ceded Embedded Derivatives [Member] | Minimum [Member] | Other Liabilities [Member] | NPR [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative liability, measurement input	0.0002
GLB Ceded Embedded Derivatives [Member] | Minimum [Member] | Other Liabilities [Member] | Volatility [Member]
Liabilities Fair Value Disclosure [Abstract]
Derivative liability, measurement input	0.01