Borrowings (Details 3) (Master Lease Agreement, USD $)	3 Months Ended
	Mar. 31, 2013	Aug. 10, 2012
Master Lease Agreement
Master Lease Agreement
Master lease facility, amount		$ 25,000,000
Master lease facility, amount available for funding leasehold improvements		14,000,000
Term of capital lease	48 months
Variable rate basis on capital lease obligation	4-year LIBOR
Ending purchase price of underlying equipment	1
Interest, margin over base rate (as a percent)	2.25%
Interest, base rate	30-day LIBOR
Amount borrowed under Credit Agreement	$ 18,200,000