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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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Amount of financing receivable originated more than five years prior to current fiscal year.

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Amount of financing receivable originated four years prior to current fiscal year.

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Amount of financing receivable originated in current fiscal year.

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Amount of financing receivable originated in fiscal year prior to current fiscal year.

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Amount of financing receivable originated three years prior to current fiscal year.

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Amount of financing receivable originated two years prior to current fiscal year.

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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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Amount, before allowance for credit loss, of financing receivable.

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Mortgage Loans, Sorted by Applicable Credit Quality Indicators (Detail) - USD ($) $ in Millions	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Jan. 01, 2020
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	$ 2,387.1		$ 2,432.1
Loan to Value Ratio Below or Equal to 65 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	1,188.9		1,189.4
Loan To Value Ratio Above 65 To 75 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	968.0		1,000.3
Loan To Value Ratio Above 75 To 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	175.5		155.8
Loan To Value Ratio Above 85 Percent
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	54.7		86.6
Originated Five or More Years before Last Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	1,075.3
Originated Four Years before Last Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	308.2
Originated Three Years before Last Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	386.0
Originated Two Years before Last Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	362.5
Originated in Fiscal Year before Latest Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	181.5
Originated in Current Fiscal Year
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	73.6
Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	1,079.4
Financing Receivable, Originated Four Years before Latest Fiscal Year	309.7
Financing Receivable, Originated Three Years before Latest Fiscal Year	388.2
Financing Receivable, Originated Two Years before Latest Fiscal Year	364.8
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	182.6
Financing Receivable, Originated in Current Fiscal Year	73.8
Financing Receivable, before Allowance for Credit Loss	2,398.5		2,445.2
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	11.4		13.1
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	805.9
Financing Receivable, Originated Four Years before Latest Fiscal Year	130.4
Financing Receivable, Originated Three Years before Latest Fiscal Year	99.3
Financing Receivable, Originated Two Years before Latest Fiscal Year	81.8
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	54.8
Financing Receivable, Originated in Current Fiscal Year	19.9
Financing Receivable, before Allowance for Credit Loss	1,192.1
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	3.2	$ 3.0	3.4	$ 3.9	$ 3.5	$ 2.8
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	131.2
Financing Receivable, Originated Four Years before Latest Fiscal Year	108.5
Financing Receivable, Originated Three Years before Latest Fiscal Year	269.7
Financing Receivable, Originated Two Years before Latest Fiscal Year	283.0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	127.8
Financing Receivable, Originated in Current Fiscal Year	53.9
Financing Receivable, before Allowance for Credit Loss	974.1
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	6.2	6.3	7.3	7.9	6.5	4.6
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	126.5
Financing Receivable, Originated Four Years before Latest Fiscal Year	37.4
Financing Receivable, Originated Three Years before Latest Fiscal Year	13.2
Financing Receivable, Originated Two Years before Latest Fiscal Year	0.0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0.0
Financing Receivable, Originated in Current Fiscal Year	0.0
Financing Receivable, before Allowance for Credit Loss	177.1
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	1.5	1.2	1.3	1.0	0.4	0.5
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	15.8
Financing Receivable, Originated Four Years before Latest Fiscal Year	33.4
Financing Receivable, Originated Three Years before Latest Fiscal Year	6.0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0.0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0.0
Financing Receivable, Originated in Current Fiscal Year	0.0
Financing Receivable, before Allowance for Credit Loss	55.2
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	0.5	$ 1.0	1.1	$ 0.4	$ 0.7	$ 0.4
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	4.1
Commercial Real Estate \| Originated Four Years before Last Fiscal Year
Mortgage Loans on Real Estate
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	1.5
Commercial Real Estate \| Originated Three Years before Last Fiscal Year
Mortgage Loans on Real Estate
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	2.2
Commercial Real Estate \| Originated Two Years before Last Fiscal Year
Mortgage Loans on Real Estate
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	2.3
Commercial Real Estate \| Originated in Fiscal Year before Latest Fiscal Year
Mortgage Loans on Real Estate
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	1.1
Commercial Real Estate \| Originated in Current Fiscal Year
Mortgage Loans on Real Estate
Financing Receivable, Allowance for Credit Losses, Mortgage Loans	0.2
AA Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	3.4		3.5
AA Credit Rating \| Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	3.4
Financing Receivable, Originated Four Years before Latest Fiscal Year	0.0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0.0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0.0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0.0
Financing Receivable, Originated in Current Fiscal Year	0.0
Financing Receivable, before Allowance for Credit Loss	3.4
A Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	493.9		510.0
A Credit Rating \| Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	337.1
Financing Receivable, Originated Four Years before Latest Fiscal Year	60.1
Financing Receivable, Originated Three Years before Latest Fiscal Year	63.7
Financing Receivable, Originated Two Years before Latest Fiscal Year	16.4
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	17.8
Financing Receivable, Originated in Current Fiscal Year	0.0
Financing Receivable, before Allowance for Credit Loss	495.1
BBB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	1,838.4		1,863.0
BBB Credit Rating \| Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	697.6
Financing Receivable, Originated Four Years before Latest Fiscal Year	239.3
Financing Receivable, Originated Three Years before Latest Fiscal Year	324.5
Financing Receivable, Originated Two Years before Latest Fiscal Year	348.4
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	164.8
Financing Receivable, Originated in Current Fiscal Year	73.8
Financing Receivable, before Allowance for Credit Loss	1,848.4
BB Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	35.7		39.4
BB Credit Rating \| Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	25.5
Financing Receivable, Originated Four Years before Latest Fiscal Year	10.3
Financing Receivable, Originated Three Years before Latest Fiscal Year	0.0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0.0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0.0
Financing Receivable, Originated in Current Fiscal Year	0.0
Financing Receivable, before Allowance for Credit Loss	35.8
B Credit Rating
Mortgage Loans on Real Estate
Mortgage Loans, Carrying Amount	15.7		$ 16.2
B Credit Rating \| Commercial Real Estate
Mortgage Loans on Real Estate
Financing Receivable, Originated Five or More Years before Latest Fiscal Year	15.8
Financing Receivable, Originated Four Years before Latest Fiscal Year	0.0
Financing Receivable, Originated Three Years before Latest Fiscal Year	0.0
Financing Receivable, Originated Two Years before Latest Fiscal Year	0.0
Financing Receivable, Originated in Fiscal Year before Latest Fiscal Year	0.0
Financing Receivable, Originated in Current Fiscal Year	0.0
Financing Receivable, before Allowance for Credit Loss	$ 15.8