Debt (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2020 USD ($) line_of_credit financial_institution	Dec. 31, 2019 USD ($)	Sep. 01, 2020 USD ($)
Line of Credit
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity	$ 800,000,000.0
Maximum incremental increase	200,000,000.0
Amount outstanding	$ 0	$ 0
Commercial Paper
Short-term Debt [Line Items]
Weighted average interest rates on average daily borrowings	0.50%	2.60%
Short-term debt	$ 0	$ 0
Debt instrument, term		317 days
Short-term debt, average outstanding amount	$ 85,200,000	$ 438,600,000
Uncommited Lines of Credit
Short-term Debt [Line Items]
Weighted average interest rates	1.30%	1.90%
Short-term debt	$ 0	$ 0
Short-term debt, average outstanding amount	1,200,000	1,900,000
EQH
Short-term Debt [Line Items]
Amount outstanding	$ 300,000,000.0	$ 560,000,000.0
Weighted average interest rates	0.20%	1.60%
Average borrowing period		57 days
Average daily borrowings	$ 503,400,000	$ 358,600,000
Weighted average interest rates on average daily borrowings	0.60%	1.60%
Revolving Credit Facility
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity	$ 200,000,000.0
Revolving Credit Facility | EQH
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity	900,000,000.0
Revolving Credit Facility | Line of Credit
Short-term Debt [Line Items]
Amount outstanding	$ 0	$ 0
Weighted average interest rates	1.50%	3.20%
Average daily borrowings	$ 14,000,000.0	$ 23,500,000
Revolving Credit Facility | EQH Uncommitted Facility
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity			$ 300,000,000.0
Amount outstanding	0
(Repayment) of EQH Facility	0
Subsidiaries | Line of Credit
Short-term Debt [Line Items]
Line of credit facility, maximum borrowing capacity	$ 175,000,000.0
Number of uncommitted lines of credit | line_of_credit	3
Number of financial institutions offering lines of credit | financial_institution	3
Number of financial institutions with stated limits | line_of_credit	2