Significant Accounting Policies - Variable Interest Entities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2014
Variable Interest Entity [Line Items]
Long-term investments	$ 23,025	$ 20,812
Proceeds from VIE	$ 183	183	$ 183
Red Oak
Variable Interest Entity [Line Items]
VIE, ownership percentage				50.00%
Initial contractual term (in years)				10 years
Amended contract extension term	5 years
Amended contract term (in years)	15 years
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Long-term investments	$ 1,289	1,089
Variable Interest Entity, Not Primary Beneficiary | Hedge fund investments
Variable Interest Entity [Line Items]
Long-term investments	463	342
Variable Interest Entity, Not Primary Beneficiary | Private equity investments
Variable Interest Entity [Line Items]
Long-term investments	601	547
Variable Interest Entity, Not Primary Beneficiary | Real estate partnerships
Variable Interest Entity [Line Items]
Long-term investments	$ 225	$ 200