Accounts Receivable Allowance for Doubtful Accounts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance, beginning of year	$ 2,693	$ 2,807	$ 3,079
Provisions	2,741	977	1,055
Charges	(1,679)	(1,091)	(1,327)
Balance, end of year	$ 3,755	$ 2,693	$ 2,807