Treasury Stock - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Jun. 30, 2012	Jul. 26, 2006	Sep. 17, 2001
Equity, Class of Treasury Stock [Line Items]
Stock authorized to repurchase under stock repurchase program		4,000,000	1,000,000
Additional stock authorized to repurchase under stock repurchase program		3,000,000
Shares repurchased during the period, shares	2,006,293
Open Market Stock Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Shares repurchased during the period, shares	249,499
Shares repurchased during the period, value	4.9
Restricted Stock
Equity, Class of Treasury Stock [Line Items]
Shares repurchased during the period, shares	70,904
Shares repurchased during the period, value	1.5