Accounts Receivable Accounts Receivable (Allowance) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at January 1	$ 1,560	$ 1,259	$ 1,722
Write-offs	(558)	(488)	(342)
Recoveries	236	139	116
Increase (decrease) in allowance	1,119	650	(237)
Balance at December 31	$ 2,357	$ 1,560	$ 1,259