Parent Company - Additional Information (Detail) - Group Inc. [Member] - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2021
Parent Company Only Financial Information [Line Items]
Noncash or Part Noncash Acquisition, Debt Assumed		$ 8,500.0
Loans exchanged for equity interest in subsidiary			$ 948.0
Trust Preferred Securities and common beneficial interests exchanged with the firm's junior subordinated debt	$ 11.2	211.0
Firm's Junior subordinated debt exchanged for Trust Preferred Securities and common beneficial interests	$ 12.5	$ 231.0

The amount of debt that an Entity assumes in acquiring a business or in consideration for an asset received in a noncash (or part noncash) acquisition. Noncash is defined as transactions during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=123431023&loc=d3e4304-108586

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=123431023&loc=d3e4313-108586

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=123431023&loc=d3e4332-108586

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration