Composition of Fixed Maturities by Maturity (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013
Available for sale, cost
Less than one year	$ 2,032.1
One to five years	8,610.3
Five to ten years	2,834.8
Ten years or greater	114.2
Total	13,591.4	[1]
Available for sale, Fair value
Less than one year	2,063.1
One to five years	8,767.3
Five to ten years	2,794.5
Ten years or greater	119.3
Total	$ 13,744.2	[1]

[1] Excludes $53.5 million related to our open interest rate swap positions.