Goodwill and Intangibles, including DAC and VOBA - Estimated Amortization Expense for VOBA and DAC in Future Fiscal Periods (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014
Schedule Of Amortization Expense And Weighted Average Lives Of Identified Intangible Assets [Line Items]
2013	$ 82.0
2014	80.7
2015	80.7
2016	80.7
2017	80.7
VOBA [Member]
Schedule Of Amortization Expense And Weighted Average Lives Of Identified Intangible Assets [Line Items]
2013	20.7
2014	44.5
2015	39.7
2016	32.5
2017	26.1
Thereafter	$ 119.2