Accounts Receivable Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of year	$ 5,826	$ 3,755	$ 2,693
Provisions	7,512	5,191	2,741
Charges	(7,125)	(3,120)	(1,679)
Balance, end of year	$ 6,213	$ 5,826	$ 3,755