Stockholders' Equity (Changes in Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' equity balance at March 31, 2015				$ 2,151,586
Tax effect of other comprehensive income items		$ (48)	$ (48)	(96)	$ (96)
Other comprehensive income (loss), net of tax		(4,965)	$ (5,310)	(3,073)	$ (2,653)
Stockholders' equity balance at September 30, 2015		1,917,121		1,917,121
Accumulated Other Comprehensive Income [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' equity balance at March 31, 2015				(14,853)
Other comprehensive income (loss) before reclassifications				(3,236)
Amounts reclassified from AOCI	[1]			259
Tax effect of other comprehensive income items				(96)
Other comprehensive income (loss), net of tax				(3,073)
Stockholders' equity balance at September 30, 2015		(17,926)		(17,926)
Foreign Currency Translation Adjustments [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' equity balance at March 31, 2015				(14,690)
Other comprehensive income (loss) before reclassifications				(3,236)
Amounts reclassified from AOCI	[1]			0
Tax effect of other comprehensive income items				0
Other comprehensive income (loss), net of tax				(3,236)
Stockholders' equity balance at September 30, 2015		(17,926)		(17,926)
Treasury Rate Lock Agreement [Member]
Changes in Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' equity balance at March 31, 2015				(163)
Other comprehensive income (loss) before reclassifications				0
Amounts reclassified from AOCI	[1]			259
Tax effect of other comprehensive income items				(96)
Other comprehensive income (loss), net of tax				163
Stockholders' equity balance at September 30, 2015		$ 0		$ 0

[1] The reclassifications out of AOCI were associated with a loss on a treasury rate lock agreement from July 2010 related to the issuance of the Company’s 2015 Notes, which was being reclassified into earnings (interest expense) over the term of the 2015 Notes until their redemption in September 2015. The effects on the respective line items of the consolidated statements of earnings impacted by the reclassifications were not material for the six months ended September 30, 2015 and 2014.