Goodwill (Key Ratios Used to Measure Goodwill of Property and Casualty Insurance Reporting Unit for Impairment) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	May 31, 2012	May 31, 2011
Annual [Member]
Goodwill [Line Items]
Average price to book		1.17	1.23
Median price to earnings		12.1	13.8
Property And Casualty Insurance Reporting Unit [Member]
Goodwill [Line Items]
Goodwill		$ 17,177	$ 17,177
Number of key ratios used	2
Fair value of the property and casualty insurance reporting unit exceeding carrying value		205.60%	48.40%