Stock-Based Compensation (Stock-Based Compensation Expense) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Stock-based compensation expense related to:
Stock-based compensation expense	$ 6,003		$ 6,237		$ 20,833		$ 19,965
Tax benefit	(2,041)		(2,134)		(7,550)		(7,428)
Stock-based compensation expense, net of tax	3,962		4,103		13,283		12,537
Stock Option [Member]
Stock-based compensation expense related to:
Stock-based compensation expense	4,962	[1]	5,179	[1]	18,734	[1]	17,860	[1]
Employee Stock Purchase Plan [Member]
Stock-based compensation expense related to:
Stock-based compensation expense	$ 1,041		$ 1,058		$ 2,099		$ 2,105

[1] Stock-based compensation expense related to stock options granted under the Company’s Equity Incentive Plan is highest during the Company’s fiscal first quarter ended June 30th relative to other quarters during the year. This is primarily due to a retirement-eligible vesting provision under the plan and the timing of the majority of the Company’s stock option awards each year during its fiscal first quarter.