Convertible Senior Notes, Warrants, and Hedges - Net Carrying Amount Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Jan. 01, 2017	Dec. 31, 2017	Jan. 01, 2017
Convertible Debt Carrying Amount [Roll Forward]
Net carrying amount, beginning of period			$ 285,541
Net carrying amount, end of period	$ 295,983		295,983
Convertible debt
Convertible Debt Carrying Amount [Roll Forward]
Contractual interest expense	1,600	$ 1,600	3,300	$ 3,400
Convertible debt | 0.875% Convertible Senior Notes Due 2022
Convertible Debt Carrying Amount [Roll Forward]
Contractual interest expense	827	836	2,480	2,480
Amortization of debt discount during the period	3,254	3,080	9,631	9,118
Amortization of debt issuance costs during the period	270	270	811	810
Total	4,351	$ 4,186	12,922	$ 12,408
Net carrying amount, beginning of period			285,541
Net carrying amount, end of period	$ 295,983		$ 295,983