Trade Accounts Receivable and Allowance for Doubtful Accounts (Tables)

12 Months Ended

Dec. 31, 2017

Receivables [Abstract]

Summary of Trade Accounts Receivable

Trade accounts receivable are recorded at the invoiced amount.

	December 31,			December 31,
	2017			2016
Trade accounts receivable	$	6,419		$	5,093
Allowance for doubtful accounts		(15	)		(15	)
Trade accounts receivable, net	$	6,404		$	5,078
Unpaid deferred revenue included in trade    accounts receivable	$	2,217		$	2,245

Customers Who Accounted for 10% or More of Trade Accounts Receivable, Net

Customers who accounted for 10% or more of trade accounts receivable, net are as follows:

	December 31,			December 31,
	2017			2016
Central Banks		47	%		57	%