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Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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Amortized cost of financing receivable originated more than five years prior to current fiscal year. Excludes net investment in lease.

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Amortized cost of financing receivable originated four years prior to current fiscal year. Excludes net investment in lease.

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Amortized cost of financing receivable originated in current fiscal year. Excludes net investment in lease.

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Amortized cost of financing receivable originated in fiscal year prior to current fiscal year. Excludes net investment in lease.

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Amortized cost of financing receivable originated three years prior to current fiscal year. Excludes net investment in lease.

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Amortized cost of financing receivable originated two years prior to current fiscal year. Excludes net investment in lease.

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The balance represents the amount of loans that are secured by real estate mortgages, offset by the reserve to cover probable credit losses on the loan portfolio.

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Amortized cost, before allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

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Mortgage Loans, Sorted by Applicable Credit Quality Indicators (Detail) - USD ($) $ in Millions	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 2,490.7		$ 2,560.4
Loan to Value Ratio Below or Equal to 65 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	1,296.3		1,346.1
Loan To Value Ratio Above 65 To 75 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	1,091.4		1,076.8
Loan To Value Ratio Above 75 To 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	90.8		114.9
Loan To Value Ratio Above 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	12.2		22.6
Originated Five or More Years before Last Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	1,161.1		981.5
Originated Four Years before Last Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	379.0		304.1
Originated Three Years before Last Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	355.3		383.0
Originated Two Years before Last Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	171.4		359.4
Originated in Fiscal Year before Latest Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	359.1		180.0
Originated in Current Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	64.8		352.4
Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	1,164.9		984.1
Financing Receivable, Originated Four Years before Latest Fiscal Year	380.6		305.5
Financing Receivable, Originated Three Years before Latest Fiscal Year	356.7		384.4
Financing Receivable, Originated Two Years before Latest Fiscal Year	171.9		360.8
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	359.9		180.7
Financing Receivable, Originated in Current Fiscal Year	65.1		353.2
Financing Receivable, before Allowance for Credit Loss	2,499.1		2,568.7
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	8.4		8.3
Commercial Real Estate \| Loan to Value Ratio Below or Equal to 65 Percent
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	824.5		779.1
Financing Receivable, Originated Four Years before Latest Fiscal Year	170.3		146.9
Financing Receivable, Originated Three Years before Latest Fiscal Year	87.3		163.0
Financing Receivable, Originated Two Years before Latest Fiscal Year	68.8		80.7
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	130.5		54.3
Financing Receivable, Originated in Current Fiscal Year	17.2		124.7
Financing Receivable, before Allowance for Credit Loss	1,298.6		1,348.7
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	2.3	$ 2.4	2.6	$ 3.2	$ 3.0	$ 3.4
Commercial Real Estate \| Loan To Value Ratio Above 65 To 75 Percent
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	242.1		115.7
Financing Receivable, Originated Four Years before Latest Fiscal Year	204.3		115.4
Financing Receivable, Originated Three Years before Latest Fiscal Year	269.4		215.4
Financing Receivable, Originated Two Years before Latest Fiscal Year	103.1		280.1
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	229.4		126.4
Financing Receivable, Originated in Current Fiscal Year	47.9		228.5
Financing Receivable, before Allowance for Credit Loss	1,096.2		1,081.5
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	4.8	4.5	4.7	6.2	6.3	7.3
Commercial Real Estate \| Loan To Value Ratio Above 75 To 85 Percent
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	91.7		89.3
Financing Receivable, Originated Four Years before Latest Fiscal Year	0.0		26.3
Financing Receivable, Originated Three Years before Latest Fiscal Year	0.0		0.0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0.0		0.0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0.0		0.0
Financing Receivable, Originated in Current Fiscal Year	0.0		0.0
Financing Receivable, before Allowance for Credit Loss	91.7		115.6
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	0.9	0.7	0.7	1.5	1.2	1.3
Commercial Real Estate \| Loan To Value Ratio Above 85 Percent
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	6.6		0.0
Financing Receivable, Originated Four Years before Latest Fiscal Year	6.0		16.9
Financing Receivable, Originated Three Years before Latest Fiscal Year	0.0		6.0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0.0		0.0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0.0		0.0
Financing Receivable, Originated in Current Fiscal Year	0.0		0.0
Financing Receivable, before Allowance for Credit Loss	12.6		22.9
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	0.4	$ 0.3	0.3	$ 0.5	$ 1.0	$ 1.1
Commercial Real Estate \| Originated Five or More Years before Last Fiscal Year
Mortgage Loans on Real Estate
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	3.8		2.6
Commercial Real Estate \| Originated Four Years before Last Fiscal Year
Mortgage Loans on Real Estate
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	1.6		1.4
Commercial Real Estate \| Originated Three Years before Last Fiscal Year
Mortgage Loans on Real Estate
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	1.4		1.4
Commercial Real Estate \| Originated Two Years before Last Fiscal Year
Mortgage Loans on Real Estate
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	0.5		1.4
Commercial Real Estate \| Originated in Fiscal Year before Latest Fiscal Year
Mortgage Loans on Real Estate
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	0.8		0.7
Commercial Real Estate \| Originated in Current Fiscal Year
Mortgage Loans on Real Estate
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	0.3		0.8
AA Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	30.2		27.3
AA Credit Rating \| Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	6.2		3.3
Financing Receivable, Originated Four Years before Latest Fiscal Year	24.0		0.0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0.0		24.0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0.0		0.0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0.0		0.0
Financing Receivable, Originated in Current Fiscal Year	0.0		0.0
Financing Receivable, before Allowance for Credit Loss	30.2		27.3
A Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	696.8		709.6
A Credit Rating \| Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	460.7		414.6
Financing Receivable, Originated Four Years before Latest Fiscal Year	78.3		68.0
Financing Receivable, Originated Three Years before Latest Fiscal Year	36.1		71.1
Financing Receivable, Originated Two Years before Latest Fiscal Year	17.4		28.9
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	81.1		17.6
Financing Receivable, Originated in Current Fiscal Year	24.4		110.6
Financing Receivable, before Allowance for Credit Loss	698.0		710.8
BBB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	1,743.3		1,802.6
BBB Credit Rating \| Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	683.2		561.2
Financing Receivable, Originated Four Years before Latest Fiscal Year	272.3		227.3
Financing Receivable, Originated Three Years before Latest Fiscal Year	320.6		283.3
Financing Receivable, Originated Two Years before Latest Fiscal Year	154.5		331.9
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	278.8		163.1
Financing Receivable, Originated in Current Fiscal Year	40.7		242.6
Financing Receivable, before Allowance for Credit Loss	1,750.1		1,809.4
BB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	20.4		20.9
BB Credit Rating \| Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	14.8		5.0
Financing Receivable, Originated Four Years before Latest Fiscal Year	6.0		10.2
Financing Receivable, Originated Three Years before Latest Fiscal Year	0.0		6.0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0.0		0.0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0.0		0.0
Financing Receivable, Originated in Current Fiscal Year	0.0		0.0
Financing Receivable, before Allowance for Credit Loss	$ 20.8		$ 21.2