Stock-Based Compensation (Stock-Based Compensation Expense) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Stock-based compensation expense related to:
Equity Incentive Plan	$ 24,892	$ 22,969	$ 21,721
Employee Stock Purchase Plan - options to purchase stock	4,069	4,084	3,887
Stock-based compensation expense	28,961	27,053	25,608
Tax benefit	(10,392)	(9,338)	(8,760)
Stock-based compensation expense, net of tax	$ 18,569	$ 17,715	$ 16,848