Schedule II - Valuation and Qualifying Accounts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance, beginning of period	$ 525		$ 910		$ 1,237
Charged to Revenues and Expenses	2,359	[1]	2,030	[1]	2,705
Deductions	(2,222)	[2]	(2,415)	[2]	(3,032)	[2]
Balance, end of period	662		525		910
Reduction to revenues	$ 2,200		$ 1,900		$ 2,600

[1] (1)Includes $2.2 million, $1.9 million and $2.6 million in 2012, 2011 and 2010, respectively, charged as a reduction to revenues.

[2] Represents accounts receivable write-offs, net of recoveries and reserve reductions credited to revenue.