Commitments and Contingencies (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Service quality penalties
Increase (decrease) in liability recorded as a reduction (increase) to revenue	$ 142	$ (1,088)
SQI penalties paid out in form of customer rebates	(345)	0
Performance assurance plan credits
Increase (decrease) in estimated reserve recorded as a reduction (increase) to revenue	(1,601)	(205)
PAP credits paid out	$ (2,084)	$ (588)