Variable Interest Entities - Narrative (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Assets	$ 183,889,800,000	$ 170,003,900,000	$ 136,828,400,000
Liabilities	171,873,000,000	158,315,600,000
Investment company, voluntary fee waived	287,800,000	36,400,000
Fair value, investments, entities that calculate net asset value per share, seed capital investments	0
Unfunded commitment related to seed capital investments	0
Tax Credit Structures
Variable Interest Entity [Line Items]
Exposure to loss from liquidity arrangements and obligations to purchase assets	0
Affordable housing tax credits and other tax benefits	87,200,000	78,900,000
Other Assets
Variable Interest Entity [Line Items]
Investments in community development projects, carrying amount, assets	959,600,000	919,600,000
Other Assets | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Assets	922,800,000	874,000,000
Other Liabilities
Variable Interest Entity [Line Items]
Investments in community development projects, carrying amount, liabilities	289,300,000	351,600,000
Other Liabilities | Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Liabilities	$ 280,500,000	$ 335,900,000