Basis of Presentation (Cash Cash Equivalents and Short-term Investments) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended		12 Months Ended	3 Months Ended
	Sep. 30, 2014	Mar. 31, 2014	Sep. 30, 2014 Money Market Funds	Mar. 31, 2014 Money Market Funds	Sep. 30, 2014 Mutual Funds	Mar. 31, 2014 Mutual Funds	Sep. 30, 2014 Commercial Paper	Mar. 31, 2014 Commercial Paper	Sep. 30, 2014 Corporate Debt	Mar. 31, 2014 Corporate Debt	Sep. 30, 2014 Municipal Securities	Mar. 31, 2014 Municipal Securities	Sep. 30, 2014 Asset Backed Securities	Mar. 31, 2014 Asset Backed Securities	Sep. 30, 2014 Mortgage Backed Securities	Sep. 30, 2014 Internatinal Government Securities	Mar. 31, 2014 Internatinal Government Securities	Sep. 30, 2014 Certificates of Deposit
Amortized Cost Basis	$ 152,133	$ 151,854	$ 22,571	$ 32,611	$ 2,000	$ 1,964	$ 18,232	$ 30,374	$ 67,902	$ 63,621	$ 5,435	$ 5,435	$ 26,038	$ 17,049	$ 6,955	$ 804	$ 800	$ 2,200
Available-for-sale Securities, Gross Unrealized Gain	88	55	0	0	0	0	5	5	69	35	3	5	6	6	0	1	5	0
Gross Unrealized Losses	(131)	(96)	0	0	(87)	(55)	(1)	0	(2)	(39)	(6)	(1)	(5)	(1)	(29)	0	0	(1)
Total available-for-sale investments, estimated fair value	152,090	151,813	22,571	32,611	1,913	1,909	18,236	30,379	67,969	63,617	5,432	5,439	26,039	17,054	6,926	805	805	2,199
Reported as:
Cash equivalents	22,571	32,611
Short-term investments	129,519	47,181
Long-term investments	0	72,021
Contractual maturities of investments:
Investments due within one year	102,300	79,792
Investments due after one year	$ 49,790	$ 72,021