Revenue and Expense - Additional Information (Details) - Parent Company [Member] - USD ($) $ in Billions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Management fee income	$ 1.7	$ 1.3
Compensation expense	$ 1.7	$ 1.3

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.

No definition available.

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration