Credit Risk (Changes in the Allowance for Doubtful Accounts) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at beginning of period	$ 267
Provision (reduction) for doubtful accounts	(60)	$ 7
Write-offs, net of amounts recovered	(29)
Balance at end of period	$ 178