Derivative Financial Instruments - Narrative (Details) - USD ($)	6 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Potential recoveries	$ 0
Cash and securities pledged as collateral by counterparties	7,000,000
Securities pledged as collateral to counterparties	6,000,000
Collateral posted under MNAs for contracts containing credit-risk contingent features	3,000,000	$ 13,000,000
Cash and securities pledged in the form of margin deposits	56,000,000
Margin deposit liabilities	$ 10,000,000