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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	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 2,476.4		$ 2,560.4
Loan to Value Ratio Below or Equal to 65 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	1,317.6		1,346.1
Loan To Value Ratio Above 65 To 75 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	1,043.3		1,076.8
Loan To Value Ratio Above 75 To 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	109.9		114.9
Loan To Value Ratio Above 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	5.6		22.6
Originated Five or More Years before Last Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	1,146.7		981.5
Originated Four Years before Last Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	377.0		304.1
Originated Three Years before Last Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	345.4		383.0
Originated Two Years before Last Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	170.4		359.4
Originated in Fiscal Year before Latest Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	357.4		180.0
Originated in Current Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	79.5		352.4
Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	1,150.7		984.1
Financing Receivable, Originated Four Years before Latest Fiscal Year	378.6		305.5
Financing Receivable, Originated Three Years before Latest Fiscal Year	346.8		384.4
Financing Receivable, Originated Two Years before Latest Fiscal Year	170.9		360.8
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	358.2		180.7
Financing Receivable, Originated in Current Fiscal Year	79.9		353.2
Financing Receivable, before Allowance for Credit Loss	2,485.1		2,568.7
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	8.7		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	812.7		779.1
Financing Receivable, Originated Four Years before Latest Fiscal Year	190.0		146.9
Financing Receivable, Originated Three Years before Latest Fiscal Year	102.3		163.0
Financing Receivable, Originated Two Years before Latest Fiscal Year	68.4		80.7
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	129.7		54.3
Financing Receivable, Originated in Current Fiscal Year	17.0		124.7
Financing Receivable, before Allowance for Credit Loss	1,320.1		1,348.7
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	2.5	$ 2.3	2.6	$ 3.2	$ 3.2	$ 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	227.4		115.7
Financing Receivable, Originated Four Years before Latest Fiscal Year	182.7		115.4
Financing Receivable, Originated Three Years before Latest Fiscal Year	244.5		215.4
Financing Receivable, Originated Two Years before Latest Fiscal Year	102.5		280.1
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	228.5		126.4
Financing Receivable, Originated in Current Fiscal Year	62.9		228.5
Financing Receivable, before Allowance for Credit Loss	1,048.5		1,081.5
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	5.2	4.8	4.7	6.2	6.2	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	110.6		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	110.6		115.6
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	0.7	0.9	0.7	1.4	1.5	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	0.0		0.0
Financing Receivable, Originated Four Years before Latest Fiscal Year	5.9		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	5.9		22.9
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	0.3	$ 0.4	0.3	$ 0.5	$ 0.5	$ 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	4.0		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	0.4		0.8
AA Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	30.1		27.3
AA Credit Rating \| Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	6.1		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	30.1		27.3
A Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	695.5		709.6
A Credit Rating \| Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	453.3		414.6
Financing Receivable, Originated Four Years before Latest Fiscal Year	78.0		68.0
Financing Receivable, Originated Three Years before Latest Fiscal Year	43.2		71.1
Financing Receivable, Originated Two Years before Latest Fiscal Year	17.3		28.9
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	80.8		17.6
Financing Receivable, Originated in Current Fiscal Year	24.2		110.6
Financing Receivable, before Allowance for Credit Loss	696.8		710.8
BBB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	1,730.6		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	676.6		561.2
Financing Receivable, Originated Four Years before Latest Fiscal Year	270.7		227.3
Financing Receivable, Originated Three Years before Latest Fiscal Year	303.6		283.3
Financing Receivable, Originated Two Years before Latest Fiscal Year	153.6		331.9
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	277.4		163.1
Financing Receivable, Originated in Current Fiscal Year	55.7		242.6
Financing Receivable, before Allowance for Credit Loss	1,737.6		1,809.4
BB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	20.2		20.9
BB Credit Rating \| Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	14.7		5.0
Financing Receivable, Originated Four Years before Latest Fiscal Year	5.9		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	$ 20.6		$ 21.2