Contingent Consideration (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended	3 Months Ended	12 Months Ended
	Apr. 30, 2011	Jun. 30, 2011	Dec. 31, 2011	Dec. 31, 2012
Contingent Consideration
Contingent consideration payment	$ 40,000
Maximum aggregate undiscounted amount of contingent consideration				19,000
Remaining contingent consideration liability adjusted through operating income		17,800	17,813
Changes in net income due to adjustment of remaining contingent consideration liability			$ 11,200