Consolidated Statements of Income and Comprehensive Income (Unaudited) (Parenthetical) (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jul. 31, 2014	Jul. 31, 2013	Jul. 31, 2014	Jul. 31, 2013
Income Statement [Abstract]
Other comprehensive income, postretirement benefits, income tax benefit	$ 12	$ 16	$ 26	$ 32