Schedule of deferred income tax assets and liabilities (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Income Tax [Abstract]
Deferred Acquisition Cost	$ 140.4	$ 97.4
Deferred Tax Liabilities for Fixed Assets	87.1	95.6
Deferred Tax Liabilities on Invested Assets	1,128.4	1,982.8
Other	55.4	64.6
Gross Deferred Tax Liability	1,411.3	2,240.4
Reserves	1,060.5	1,919.2
Employee Benefits	246.0	254.0
Other	14.3	5.2
Gross Deferred Tax Asset	1,320.8	2,178.4
Less: Valuation Allowance	1.3	0.0
Net Deferred Tax Asset	1,319.5	2,178.4
Net Deferred Tax Liability	$ 91.8	$ 62.0