Income Taxes (Effective Income Tax Rate Reconciliation) (Details)	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Income Tax Disclosure [Abstract]
Taxes at U.S. federal statutory rate	35.00%	35.00%	35.00%
Increase (decrease) in income taxes resulting from:
State income taxes, net of federal benefit	2.10%	2.90%	2.50%
Stock-based compensation expense	0.10%	0.20%	0.20%
State tax effect of corporate reorganization	0.00%	0.00%	(0.70%)
Domestic production activities deduction	(1.00%)	(0.90%)	(0.40%)
Other, net	0.20%	0.10%	(0.30%)
Effective income tax rate	36.40%	37.30%	36.30%