Related Parties Narrative (Details) - Preferred Shares - OppenheimerFunds $ in Millions		4 Months Ended
Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)
Related Party Transactions [Line Items]
Stock consideration	$ 4,010.5	$ 4,000.0
MassMutual
Related Party Transactions [Line Items]
Approximate stake help in common stock of combined firm (percent)	16.70%	16.70%

Amount of equity interests of the acquirer, including instruments or interests issued or issuable in consideration for the business combination.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6613-128477

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6578-128477

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