Financial Instruments - Investment (Details) $ in Thousands	6 Months Ended	12 Months Ended
	Dec. 31, 2016 USD ($) position	Jun. 30, 2016 USD ($) position	Dec. 31, 2015 USD ($)	Jun. 30, 2015 USD ($)
Cash, cash equivalents and short-term investments
Amortized Cost	$ 108,465	$ 167,025
Gross Unrealized Gains		8
Gross Unrealized Losses	(85)	(23)
Cash and Cash Equivalents	69,472	119,771	$ 88,451	$ 79,551
Short-term Investments	38,908	47,239
Other-than-temporary impairments	0	0
Amortized Cost
Due in 1 year or less	14,122
Due in 1-2 years	26,993
Total Amortized Cost	41,115
Estimated Fair Value
Due in 1 year or less	14,110
Due in 1-2 years	26,920
Available-for-sale Securities	41,030
Gross Unrealized Losses
Less Than 12 Months	(12)	(3)
12 Months or Greater	(73)	(20)
Total	(85)	(23)
Estimated Fair Value
Less Than 12 Months	11,988	6,325
12 Months or Greater	26,920	23,148
Total	$ 38,908	$ 29,473
Number of positions held in an unrealized loss position | position	13	11
U.S. government agency securities
Gross Unrealized Losses
Less Than 12 Months	$ (12)
12 Months or Greater	(73)	$ (17)
Total	(85)	(17)
Estimated Fair Value
Less Than 12 Months	11,988
12 Months or Greater	26,920	19,988
Total	38,908	19,988
Corporate debt securities
Gross Unrealized Losses
Less Than 12 Months		(3)
12 Months or Greater		(3)
Total		(6)
Estimated Fair Value
Less Than 12 Months		6,325
12 Months or Greater		3,160
Total		9,485
Cash
Cash, cash equivalents and short-term investments
Amortized Cost	67,350	95,906
Cash and Cash Equivalents	67,350	95,906
Level 1
Cash, cash equivalents and short-term investments
Amortized Cost		13,362
Cash and Cash Equivalents		13,362
Level 1 | Money market funds
Cash, cash equivalents and short-term investments
Amortized Cost	2,122	13,362
Cash and Cash Equivalents	2,122	13,362
Level 2
Cash, cash equivalents and short-term investments
Amortized Cost		57,757
Gross Unrealized Gains		8
Gross Unrealized Losses		(23)
Cash and Cash Equivalents		10,503
Short-term Investments		47,239
Level 2 | Commercial paper
Cash, cash equivalents and short-term investments
Amortized Cost		14,704
Cash and Cash Equivalents		8,938
Short-term Investments		5,766
Level 2 | U.S. government agency securities
Cash, cash equivalents and short-term investments
Amortized Cost	38,993	28,000
Gross Unrealized Gains		7
Gross Unrealized Losses	(85)	(17)
Short-term Investments	$ 38,908	27,990
Level 2 | U.S. treasury securities
Cash, cash equivalents and short-term investments
Amortized Cost		3,997
Gross Unrealized Gains		1
Short-term Investments		3,998
Level 2 | Municipal debt securities
Cash, cash equivalents and short-term investments
Amortized Cost		1,565
Cash and Cash Equivalents		1,565
Level 2 | Corporate debt securities
Cash, cash equivalents and short-term investments
Amortized Cost		9,491
Gross Unrealized Losses		(6)
Short-term Investments		$ 9,485