Other Financial Statements Details Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Mar. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable amounts	$ 555,254	$ 480,457
Less allowance for doubtful accounts	2,119	2,084
Accounts receivable, net	553,135	478,373
Trade Accounts Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable amounts	547,572	473,238
Other Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Receivable amounts	$ 7,682	$ 7,219