Income Taxes (Reconciliation of Taxes Provided to Federal Statutory Rate) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Income Taxes Reconciliation Of Taxes Provided To Federal Statutory Rate Details
Tax provision at statutory rate									$ (11,790)	$ (1,652)	$ (2,029)
State income taxes before valuation allowance, net of federal effect									(1,042)	108	9
Foreign tax rate differential									(1,188)	885	(769)
Research and development credits									(2,189)	(1,484)	(1,253)
Change in valuation allowance									56,663	(287)	(1,555)
Compensation/option differences									(4,965)	(246)	(471)
Tax Act rate change impact									1,132	0	0
Non-deductible compensation									22,630	1,079	944
Acquisition costs									0	54	230
Expiring California loss carry-forwards									0	0	1,626
Foreign loss not benefited									6,847	780	2,342
Other									196	637	79
Total income tax provision (benefit)	$ 142	$ 70,842	$ (3,453)	$ (1,236)	$ (178)	$ 30	$ (15)	$ 37	$ 66,294	$ (126)	$ (847)