Notes Payable and Long-Term Debt - Term Debt - Narrative (Details) $ in Thousands									3 Months Ended
	Mar. 31, 2018 USD ($)	Mar. 30, 2018 USD ($)	Sep. 28, 2017 USD ($)	Feb. 27, 2017 USD ($)	Jun. 25, 2016 USD ($)	Jun. 24, 2016 USD ($)	May 27, 2015 TWD ($)	May 27, 2015 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2016 TWD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($)	Jun. 14, 2016 USD ($)
Repayments of outstanding balance			$ 11,200						$ 55,583
Notes payable and long-term debt	$ 65,154								65,154			$ 49,559
Unused borrowing capacity	42,600								42,600			1,000
Restricted cash, investments or security deposit associated with loan facilities	$ 0								0			$ 0
One Month LIBOR Rate
Interest rate description	LIBOR Borrowing Rate plus 1.88%
Basis spread on variable rate	1.88%
Letter of Credit
Revolving line of credit maximum borrowing capacity	$ 10,000								10,000
East West Bank and Comerica Bank | London Interbank Offered Rate (LIBOR) | Modification Agreement
Interest rate description						LIBOR Borrowing Rate plus 2.0%
Basis spread on variable rate					2.00%	2.00%
East West Bank and Comerica Bank | One Month LIBOR Rate | Modification Agreement
Interest rate description						one-month LIBOR Borrowing Rate plus 2.75%
Basis spread on variable rate						2.75%
East West Bank and Comerica Bank | First Amendment | London Interbank Offered Rate (LIBOR) | Modification Agreement
Interest rate description					LIBOR Borrowing Rate plus 2.0%
East West Bank | Modification Agreement
Revolving line of credit maximum borrowing capacity													$ 22,000
China Construction Bank
Revolving line of credit maximum borrowing capacity	13,200								13,200
Chailease Finance Co. Ltd. | Finance Lease 1
Note payable	200								200
Lease purchase price							$ 180,148,532	$ 6,000
Initial payment amount							$ 60,148,532	$ 2,000
Financial lease term							3 years	3 years
Chailease Finance Co. Ltd. | Finance Lease 1 | Minimum
Lease payment range price							$ 3,322,413	$ 100
Chailease Finance Co. Ltd. | Finance Lease 1 | Maximum
Lease payment range price							$ 3,784,000	$ 100
Chailease Finance Co. Ltd. | Finance Lease 2
Lease purchase price										$ 312,927,180	$ 10,100
Financial lease term										3 years	3 years
Financial lease Interest rate										4.00%	4.00%
Chailease Finance Co. Ltd. | Finance Lease 2 | Minimum
Initial payment amount										$ 62,927,180
Lease payment range price										6,772,500	$ 200
Chailease Finance Co. Ltd. | Finance Lease 2 | Maximum
Initial payment amount											2,000
Lease payment range price										$ 7,788,333	$ 300
Branch Banking and Trust Company | First Credit Facility
Revolving line of credit maximum borrowing capacity			$ 50,000
Term of loan			3 years
Branch Banking and Trust Company | First Credit Facility | One Month LIBOR Rate
Basis spread on variable rate			1.50%
Branch Banking and Trust Company | Line of credit
Revolving line of credit maximum borrowing capacity		$ 60,000
Notes payable and long-term debt	38,400								$ 38,400
Branch Banking and Trust Company | Line of credit | One Month LIBOR Rate
Interest rate description		one-month LIBOR plus
Branch Banking and Trust Company | Line of credit | One Month LIBOR Rate | Minimum
Basis spread on variable rate		1.40%
Branch Banking and Trust Company | Line of credit | One Month LIBOR Rate | Maximum
Basis spread on variable rate		2.00%
Revolving Line of Credit | East West Bank and Comerica Bank | First Amendment
Revolving line of credit maximum borrowing capacity					$ 40,000	$ 25,000
Draw down period									1 year
Term of revolving credit facility									5 years
Revolving Line of Credit | East West Bank and Comerica Bank | First Amendment | London Interbank Offered Rate (LIBOR)
Interest rate description						LIBOR Borrowing Rate plus 2.75% or 3.0%
Revolving Line of Credit | East West Bank and Comerica Bank | First Amendment | London Interbank Offered Rate (LIBOR) | Minimum
Basis spread on variable rate						2.75%
Revolving Line of Credit | East West Bank and Comerica Bank | First Amendment | London Interbank Offered Rate (LIBOR) | Maximum
Basis spread on variable rate						3.00%
Term Loan | East West Bank and Comerica Bank
Revolving line of credit maximum borrowing capacity	5,000								$ 5,000
Repayments of outstanding balance				$ 2,800
Revolving line of credit, maturity date									Jul. 31, 2019
Term Loan | East West Bank and Comerica Bank | First Amendment
Revolving line of credit maximum borrowing capacity	10,000								$ 10,000
Term Loan | Branch Banking and Trust Company
Notes payable and long-term debt	21,500								21,500
Term Loan | Branch Banking and Trust Company | One Month LIBOR Rate
Interest rate description		one-month LIBOR plus
Term Loan | Branch Banking and Trust Company | One Month LIBOR Rate | Minimum
Basis spread on variable rate		1.15%
Term Loan | Branch Banking and Trust Company | One Month LIBOR Rate | Maximum
Basis spread on variable rate		2.00%
Equipment Term Loan | East West Bank and Comerica Bank | First Amendment
Revolving line of credit maximum borrowing capacity	10,000								10,000
Capital expenditure loan | Branch Banking and Trust Company
Revolving line of credit maximum borrowing capacity		$ 26,000
Term of revolving credit facility		5 years
Notes payable and long-term debt	$ 5,100								$ 5,100
Capital expenditure loan | Branch Banking and Trust Company | One Month LIBOR Rate
Interest rate description		one-month LIBOR plus
Capital expenditure loan | Branch Banking and Trust Company | One Month LIBOR Rate | Minimum
Basis spread on variable rate		1.30%
Capital expenditure loan | Branch Banking and Trust Company | One Month LIBOR Rate | Maximum
Basis spread on variable rate		2.00%
Real estate term loan | Branch Banking and Trust Company
Revolving line of credit maximum borrowing capacity		$ 21,500
Term of revolving credit facility		70 months