Repurchase of Common Stock (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended			12 Months Ended
	Sep. 30, 2012	Oct. 13, 2008	Sep. 30, 2005	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2011	Sep. 30, 2011
Equity, Class of Treasury Stock [Line Items]
Interest rate of notes repurchased (in hundredths)	7.50%	4.50%					4.50%
Stock repurchase program, authorized amount		$ 30,000	$ 9,864
Value of repurchased principal		35,920		14,076
Repurchased value of repurchased principal	3,019	28,112		11,696		45,924
Stock repurchase program, remaining authorized repurchase amount	$ 18,304				$ 1,888