Short-term and Long-term Obligations - Bank of America (Details)	1 Months Ended
	Apr. 30, 2018 USD ($)	Jun. 30, 2016 USD ($) building	Jun. 30, 2015 USD ($) building	Jun. 30, 2017 USD ($)	May 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Short-term Debt [Line Items]
Debt, total outstanding borrowings		$ 93,589,000		$ 161,920,000
Line of credit | Revolving Credit Facility
Short-term Debt [Line Items]
Debt, total outstanding borrowings		$ 72,299,000		$ 102,199,000
Bank of America | Bank of America 2015 Credit Agreement | Term loan | Secured debt
Short-term Debt [Line Items]
Credit facility, term			5 years
Debt, face amount			$ 14,000,000
Number of buildings as collateral | building			3
Bank of America | Bank of America 2015 Credit Agreement | Term loan | Secured debt | LIBOR
Short-term Debt [Line Items]
Credit facility, basis spread on variable rate (as a percent)			1.50%
Bank of America | Bank of America 2015 Credit Agreement | Line of credit | Revolving Credit Facility
Short-term Debt [Line Items]
Credit facility, maximum borrowing capacity			$ 65,000,000
Bank of America | Bank of America 2016 Credit Agreement | Minimum
Short-term Debt [Line Items]
Interest rate (as a percent)		1.02%		1.61%
Bank of America | Bank of America 2016 Credit Agreement | Maximum
Short-term Debt [Line Items]
Interest rate (as a percent)		1.96%		2.46%
Bank of America | Bank of America 2016 Credit Agreement | Line of credit | Revolving Credit Facility
Short-term Debt [Line Items]
Collateral amount				$ 1,168,600,000
Debt, total outstanding borrowings		$ 62,200,000		83,200,000
Bank of America | Bank of America 2016 Credit Agreement | Term loan | Secured debt
Short-term Debt [Line Items]
Credit facility, term			5 years
Debt, face amount		$ 50,000,000
Number of buildings as collateral | building		7
Collateral amount				67,900,000
Debt, total outstanding borrowings		$ 900,000		40,000,000
Bank of America | Bank of America 2016 Credit Agreement | Term loan | Secured debt | LIBOR
Short-term Debt [Line Items]
Credit facility, basis spread on variable rate (as a percent)		1.25%
Bank of America | Bank of America 2016 Credit Agreement | Line of credit | Revolving Credit Facility
Short-term Debt [Line Items]
Credit facility, maximum borrowing capacity		$ 55,000,000
Credit facility, remaining borrowing capacity				$ 21,800,000
Bank of America | Bank of America 2016 Credit Agreement | Line of credit | Revolving Credit Facility | Super Micro Computer, Taiwan
Short-term Debt [Line Items]
Credit facility, maximum borrowing capacity		$ 10,000,000				$ 20,000,000
Credit facility, basis spread on variable rate (as a percent)			0.90%
Bank of America | Bank of America 2016 Credit Agreement | Line of credit | Revolving Credit Facility | LIBOR
Short-term Debt [Line Items]
Credit facility, basis spread on variable rate (as a percent)		1.25%
LIBOR rate (as a percent)				1.04%
Bank of America | Bank of America 2016 Credit Agreement | Line of credit | Letter of credit
Short-term Debt [Line Items]
Credit facility, maximum borrowing capacity		$ 5,000,000
Credit facility, basis spread on variable rate (as a percent)		1.25%
Bank of America | Bank of America 2016 Amended Credit Agreement | Line of credit | Revolving Credit Facility
Short-term Debt [Line Items]
Credit facility, maximum borrowing capacity					$ 85,000,000
Bank of America | Bank of America loan and security agreement | Line of credit | Revolving Credit Facility
Short-term Debt [Line Items]
Credit facility, maximum borrowing capacity				$ 155,000,000
Bank of America | Bank of America loan and security agreement | Line of credit | Revolving Credit Facility | Subsequent event
Short-term Debt [Line Items]
Credit facility, maximum borrowing capacity	$ 250,000,000
Bank of America | Bank of America loan and security agreement | Line of credit | Revolving Credit Facility | Revolving Credit Facility | Forecast
Short-term Debt [Line Items]
Credit facility, maximum borrowing capacity	$ 400,000,000
Credit facility, term	5 years
Bank of America | Bank of America loan and security agreement | Line of credit | Revolving Credit Facility | Revolving Credit Facility | Subsequent event
Short-term Debt [Line Items]
Credit facility, term	5 years
Bank of America | Bank of America loan and security agreement | Line of credit | Revolving Credit Facility | LIBOR | Subsequent event
Short-term Debt [Line Items]
Credit facility, basis spread on variable rate (as a percent)	2.75%
Bank of America | Bank of America loan and security agreement | Line of credit | Revolving Credit Facility | LIBOR | Minimum | Revolving Credit Facility | Forecast
Short-term Debt [Line Items]
Credit facility, basis spread on variable rate (as a percent)	1.50%
Bank of America | Bank of America loan and security agreement | Line of credit | Revolving Credit Facility | LIBOR | Maximum | Revolving Credit Facility | Forecast
Short-term Debt [Line Items]
Credit facility, basis spread on variable rate (as a percent)	2.00%