Fair Value Measurements (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Roll forward of the fair value of the asset, where fair value is determined by Level 3 inputs
Balance at the beginning of the period	$ 3,379
Expense recognized	(4,080)
Additions	398	3,482,000
Change in fair value	710	(103)
Balance at the end of the period	407	3,379
Roll forward of the fair value of the liabilities, where fair value is determined by Level 3 inputs
Balance at the beginning of the period	10,920
Additions	11,763	10,759
Change in fair value	2,779	161
Balance at the end of the period	$ 25,462	$ 10,920