Receivables and Allowance for Doubtful Receivables (Allowance for Doubtful Receivables Rollforward) (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 beginning of year	$ 4,542	$ 2,346	$ 3,215
Charged to costs and expenses	6,359	3,994	2,370
Charged to other accounts	0	0	(446)
Write-offs net of recoveries	7,271	1,798	2,793
Balance at end of year	$ 3,630	$ 4,542	$ 2,346