Employee Benefit Arrangements - Plan Assets, Allocation (Details) - Pension Plan	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	100.00%	100.00%
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	37.50%	42.60%
Equity securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target allocation range, minimum	14.00%	37.00%
Equity securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target allocation range, minimum	40.00%	65.00%
Large-cap domestic
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	18.30%	23.00%
Small/Mid-cap domestic
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	5.90%	6.10%
International Commingled Funds
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	12.00%	11.70%
Other
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	1.30%	1.80%
Debt securities
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	54.50%	46.90%
Debt securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target allocation range, minimum	54.00%	30.00%
Debt securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target allocation range, minimum	82.00%	50.00%
U.S. Treasuries, short term investments, cash and futures
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	5.40%	3.00%
U.S. government agencies and authorities
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	5.00%	8.20%
U.S. corporate, state and municipalities
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	40.80%	31.60%
Foreign securities
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	3.30%	4.10%
Other fixed maturities
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	0.00%	0.00%
Other investments
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	8.00%	10.50%
Other investments | Minimum
Defined Benefit Plan Disclosure [Line Items]
Target allocation range, minimum	6.00%	6.00%
Other investments | Maximum
Defined Benefit Plan Disclosure [Line Items]
Target allocation range, minimum	14.00%	14.00%
Hedge funds
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	3.90%	4.80%
Real estate
Defined Benefit Plan Disclosure [Line Items]
Actual allocation	4.10%	5.70%