Investments AFS (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Mar. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amount of short-term investments	$ 1,266		$ 353,284
Amount of long-term investments	0		118,549
Proceeds for sale of available-for-sale securities	470,600	$ 89,200
Realized gain on available-for-sale securities	(82)	$ 13,959
Available-for-sale securities			471,833
Corporate bonds and debt
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities			1,000
Marketable equity securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities	$ 1,266		$ 2,203