Summary of Significant Accounting Policies Impairment of long lived assets (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Impairment of long lived assets [Abstract]
Impairment of Long-Lived Assets Held-for-use	$ 0	$ 0	$ 0