CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 428,534	$ 319,564	$ 444,081
Other comprehensive income (loss):
Foreign currency translation adjustments, net of zero tax	45,618	(1,324)	17,846
Unrealized gain (loss) on derivative instruments and other, net of zero tax	(3,320)	9,096	26,744
Comprehensive income	$ 470,832	$ 327,336	$ 488,671