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
Allowance for doubtful accounts, sales returns and cash discounts
Changes to valuation allowance
Balance at beginning of period	$ 1,893	$ 1,870	$ 2,130
Charged to cost and expenses	9,148	8,368	7,535
Deductions	(9,611)	(8,345)	(7,795)
Balance at end of period	1,430	1,893	1,870
Allowance on Deferred Tax Assets
Changes to valuation allowance
Balance at beginning of period	7,592	4,003	432
Charged to cost and expenses	6,142	3,589	3,571
Deductions	(1,155)
Balance at end of period	$ 12,579	$ 7,592	$ 4,003