Liability for Unpaid Claims - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Impairment of Deferred Acquisition Costs	$ 289.8	$ 0	$ 0
Long-term Care
Reserve Increase Due to Unlocking	573.6
Claim Reserve Total [Member] | Long-term Care
Reserve Increase Due to Unlocking	248.1
Claim Reserve Total [Member] | Individual Disability Closed Block
Reserve Increase Due to Unlocking	183.5
Claim Reserve Prior Year [Member] | Long-term Care
Reserve Increase Due to Unlocking	215.0
Claim Reserve Prior Year [Member] | Individual Disability Closed Block
Reserve Increase Due to Unlocking	$ 176.0