Investments, Investment Commitments (Details) - Investments in Assets Requiring Future Purchase, Sale or Funding Commitments [Member] $ in Millions	Mar. 31, 2021 USD ($)
Investment Commitments [Abstract]
Commitments to purchase or fund investments	$ 1,400
Commitments to sell investments	$ 100

Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

No definition available.

Name:	us-gaap_OtherCommitment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant