Valuation and Qualifying Accounts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Allowance for Doubtful Accounts [Roll Forward]
Beginning of period	$ 1,753	$ 1,347	$ 1,690
Bad debt expense	1,628	3,363	2,074
Charged to other accounts	316	259	(617)
Deductions	(1,660)	(3,216)	(1,800)
End of period	$ 2,037	$ 1,753	$ 1,347