Postretirement Obligations - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended				42 Months Ended	1 Months Ended	12 Months Ended
	Dec. 31, 2010	Sep. 30, 2012	Sep. 30, 2013 SERP Agreements	Sep. 30, 2012 SERP Agreements	Sep. 30, 2011 SERP Agreements	Sep. 30, 2012 SERP Agreements	Dec. 31, 2010 SERP Agreements Mr. Matthias	Sep. 30, 2013 SERP Agreements Mr. Matthias	Sep. 30, 2012 SERP Agreements Mr. Matthias	Sep. 30, 2011 SERP Agreements Mr. Matthias
Defined Benefit Plan Disclosure [Line Items]
Annual retainer paid under Agreement		$ 200,000
SERP Agreement benefits paid to former CEO			150,000	600,000	4,166,000	3,960,000	4,166,000	150,000	600,000	750,000
Company received a distribution of the remaining assets	$ 1,504,000