Investments - Reconciliation of Other than Temporary Impairment on Fixed Maturity (Detail) (USD $)	3 Months Ended		6 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Investments, Debt and Equity Securities [Abstract]
Document Period End Date			Mar. 31, 2014
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, Additional Credit Losses	$ 0	$ 0	$ 0	$ 0
Balance at the beginning of the period	2,700,000	2,700,000	2,700,000	2,700,000
Increases attributable to credit losses on securities:
Other-than-temporary impairment was not previously recognized	0	0	0	0
Balance at the end of the period	$ 2,700,000	$ 2,700,000	$ 2,700,000	$ 2,700,000