Commitments and Contingencies (Details)	1 Months Ended	12 Months Ended
	Sep. 30, 2016 USD ($) item	Dec. 31, 2015 USD ($)
Commitments and contingencies
Bank guarantees primarily for customer advances	$ 130,900,000
Revolving Loans
Commitments and contingencies
Bank guarantees primarily for customer advances	$ 130,900,000	$ 137,700,000
Korea
Commitments and contingencies
Sales to customers as a percentage of total revenue		2.00%
KFTC investigation
Commitments and contingencies
Number of bids under investigation | item	3
Fine assessed	$ 15,000