Reportable Operating Segments - Reconciliation (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Reconciliations of total assets from reportable segments to the condensed consolidated balance sheets
Cash and cash equivalents	$ 429,970	$ 291,764	$ 245,956	$ 225,143
Deferred tax assets, net	38,381	44,708
Total assets	1,264,379	1,191,780
Reportable segments
Reconciliations of total assets from reportable segments to the condensed consolidated balance sheets
Total assets	582,360	606,058
Unallocated overhead costs
Reconciliations of total assets from reportable segments to the condensed consolidated balance sheets
Cash and cash equivalents	429,970	291,764
Deferred tax assets, net	38,381	44,708
Unallocated other corporate assets	$ 213,668	$ 249,250