Liability for Unpaid Claims - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Impairment of Deferred Acquisition Costs	$ 0	$ 196.0	$ 0
Claim Reserve Total [Member] | Long-term Care
Impairment of Deferred Acquisition Costs		573.6
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