Stock-Based Compensation (Stock-Based Compensation Expense) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Stock-based compensation expense related to:
Stock-based compensation expense		$ 5,922	$ 6,003	$ 19,572	$ 20,833
Tax benefit		(1,986)	(2,041)	(6,950)	(7,550)
Stock-based compensation expense, net of tax		3,936	3,962	12,622	13,283
Equity Incentive Plan [Member] | Stock Option [Member]
Stock-based compensation expense related to:
Stock-based compensation expense	[1]	4,990	4,962	17,485	18,734
Employee Stock Purchase Plan [Member] | Stock Option [Member]
Stock-based compensation expense related to:
Stock-based compensation expense		$ 932	$ 1,041	$ 2,087	$ 2,099

[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.