Investments - Summary of Maximum Loss Exposure (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Assets	$ 205,670	$ 202,771
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	45,130	40,479
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets	40,697	37,318
Investment funds | Investments, excluding investments in Related Party
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	1,605	1,265
Investment funds | Investments, excluding investments in Related Party | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets	966	803
Related Party | Investment funds
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	8,664	7,989
Related Party | Investment funds | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets	5,899	5,284
Debt Securities [Member] | Investments, excluding investments in Related Party
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	25,009	23,027
Debt Securities [Member] | Investments, excluding investments in Related Party | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets	25,324	23,325
Debt Securities [Member] | Related Party
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	9,738	8,126
Debt Securities [Member] | Related Party | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets	8,394	7,834
Equity securities | Related Party
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	114	72
Equity securities | Related Party | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets	$ 114	$ 72