Commercial Real Estate Loan Types (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Commercial Mortgages
Apartment/ Multi-family	$ 784.8	$ 770.1
Office	866.1	830.4
Retail	698.1	683.3
Industrial/ Warehouse	359.7	310.5
Other	457.6	442.3
Total Commercial Mortgages	3,166.3	3,036.6
Construction, Acquisition and Development Loans	445.0	392.8
Single Family Investment	179.6	147.4
Other Commercial Real Estate Related	211.6	272.0
Total Commercial Real Estate Loans	$ 4,002.5	$ 3,848.8

Commercial Mortgages [Abstract]

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Loans Receivable Commercial Construction Acquisition And Development

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Loans Receivable, Commercial Real Estate, Commercial Mortgage, Apartments And Multi Family

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Loans Receivable, Commercial Real Estate, Commercial Mortgage, Industrial And Warehouse

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Loans Receivable, Commercial Real Estate, Commercial Mortgage, Office

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Loans Receivable, Commercial Real Estate, Commercial Mortgage, Other

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Loans Receivable, Commercial Real Estate, Commercial Mortgage, Retail

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Amount before allowance of mortgage loans on existing land or building. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5066-111524

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(a)(3))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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Amount before allowance of commercial loans issued to businesses to acquire, develop, construct, improve, or refinance land or building. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(a))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(c))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5066-111524

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