Adoption of ASU 2018-12 - Summary of Changes in Net Asset Position of Ceded MRBs (Details) - Accounting Standards Update 2018-12 $ in Millions	Dec. 31, 2020 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ceded MRBs, Net	$ 6,539
Retirement Plan Services
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ceded MRBs, Net	11
Cumulative effect from adoption of new accounting standards | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ceded MRBs, Net	5,710
Cumulative effect from adoption of new accounting standards | Retained Earnings | Retirement Plan Services
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ceded MRBs, Net	10
As Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ceded MRBs, Net	829
As Previously Reported | Retirement Plan Services
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ceded MRBs, Net	1
Variable Annuities
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ceded MRBs, Net	6,528
Variable Annuities | Cumulative effect from adoption of new accounting standards | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ceded MRBs, Net	5,700
Variable Annuities | As Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ceded MRBs, Net	$ 828