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 [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$ (464)		$ (593)		$ (541)
Additions Charged to Costs and Expenses	(545)	[1]	(12)	[1]	(193)	[1]
Deduction	117	[2]	141	[2]	141	[2]
Balance at End of Year	(892)		(464)		(593)
Valuation Allowance of Deferred Tax Assets [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	(361)		0		0
Additions Charged to Costs and Expenses	(864)	[3]	(361)	[3]	0	[3]
Deduction	0		0		0
Balance at End of Year	$ (1,225)		$ (361)		$ 0

[1] We record a bad debt provision based upon historical experience and a review of individual customer balances.

[2] When an individual customer balance becomes impaired and is deemed uncollectible a deduction is made against the allowance for uncollectible accounts.

[3] We record a valuation allowance against a deferred tax asset when it is determined that it is more likely than not that the deferred tax asset will not be realized.