Summary of Significant Accounting Policies - Credit Line (Details) (Wells Fargo [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 12, 2011
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		2.50%
Line of Credit Facility, Interest Rate Description	above one or three month LIBOR
Line of Credit Facility, Collateral Fees	5
Letters of Credit Outstanding, Amount	$ 0.1
Revolving Credit Facility [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		5
Revolving Credit Facility [Member] | Letter of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		2