Stock-Based Compensation (Stock-Based Compensation Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Stock-based compensation expense related to:
Stock-based compensation expense	$ 27,757	$ 30,027	$ 28,961
Tax benefit	(9,850)	(10,624)	(10,392)
Stock-based compensation expense, net of tax	17,907	19,403	18,569
Stock Options [Member]
Stock-based compensation expense related to:
Stock-based compensation expense	24,464	25,935	24,892
Employee Stock Purchase Plan [Member]
Stock-based compensation expense related to:
Stock-based compensation expense	$ 3,293	$ 4,092	$ 4,069