Fair Value of Financial Instruments - Additional Information (Detail) (USD $)	3 Months Ended			6 Months Ended
	Mar. 31, 2013	Apr. 01, 2012		Mar. 31, 2013	Apr. 01, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Percentage of male contractholder				50.00%
Percentage of female contractholder				50.00%
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount		$ 0			$ 0
Transfers, assets, level 2 to 1	0	0		0	0
Transfers, liabilities, level 1 to 2	0	0		0	0
Transfers, liabilities, level 2 to 1	0	0		0	0
Net transfer level 3	0	10,900,000	[1]	0	10,900,000	[1]
Asset-backed and Hybrid Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	38,900,000			53,000,000
Corporate and Non-Agency Residential Mortgage-Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		$ 2,300,000			$ 12,600,000

[1] The net transfers in and out of Level 3 during the three and six months ended April 1, 2012 was exclusively to or from Level 2.