Accounts Receivable Activity in Accounts Receivable Reserves (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]
Beginning balance	$ 3,807	$ 4,555	$ 5,232
Charges to income from operations	17,900	15,599	16,165
Write-offs	(486)	(47)	(420)
Collections from cash basis customers	(17,518)	(16,300)	(16,422)
Ending balance	$ 3,703	$ 3,807	$ 4,555