Concentrations of Credit Risk - Commercial Real Estate Loans (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Commercial Mortgages
Lease Financing, net	$ 65.6	$ 90.7
Mortgages
Commercial Mortgages
Office	754.3	811.2
Apartment/ Multi-family	646.5	490.7
Retail	573.3	529.7
Industrial/ Warehouse	278.0	254.9
Other	420.1	426.6
Lease Financing, net	2,672.2	2,513.1
Real Estate
Commercial Mortgages
Lease Financing, net	3,378.0	3,228.8
Construction, Acquisition and Development Loans	432.1	420.6
Single Family Investment	95.5	127.0
Other Commercial Real Estate Related	$ 178.2	$ 168.1