Discontinued Operations (Narrative) (Details) - Discontinued Operations, Disposed of by Sale - BlackRock, Inc.	May 18, 2020 shares
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued operations, number of shares contributed	500,000
Registered Secondary Offering
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	31,600,000

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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