Commitments and Contingencies (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Commitments and Contingencies (Textual) [Abstract]
Rental expense	$ 0.7	$ 0.6
Future lease obligations under sublease arrangements	1.4
Settlement days of bond transaction	Within one to three trading days
Collateral deposit	0.9
Standby Letters of Credit [Member]
Loss Contingencies [Line Items]
Contingent obligation for standby letter of credit issued to Landlord	$ 1.7