Summary of Open Tax Years (Detail)	9 Months Ended
	Dec. 31, 2012
U.S. federal | Maximum
Income Tax Examination [Line Items]
Open tax years	2011
U.S. federal | Minimum
Income Tax Examination [Line Items]
Open tax years	2008
States | Maximum
Income Tax Examination [Line Items]
Open tax years	2011
States | Minimum
Income Tax Examination [Line Items]
Open tax years	2007