Commitments and Contingencies (Details Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Commitments and Contingencies (Textual) [Abstract]
Rental expense	$ 2.6	$ 2.5	$ 2.7
Future lease obligations under sublease arrangements	1.1
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	$ 1.5