Short-term and Long-term Debt - Line of Credit (Details) (Revolving line of credit [Member], USD $)	Dec. 31, 2012	Dec. 31, 2011
Line of Credit Facility [Line Items]
Line of credit amount	$ 30,000,000
Line of credit outstanding balance	0	0
Tangible net worth	308,512,000
Liquid Assets	72,268,000
Minimum [Member]
Line of Credit Facility [Line Items]
Minimum tangible net worth required	175,000,000
Liquid assets	$ 25,000,000
Selected LIBOR rate [Member]
Line of Credit Facility [Line Items]
Interest rate on line of credit, variable rate	2.50%
LIBOR for a fixed rate term [Member]
Line of Credit Facility [Line Items]
Interest rate on line of credit, variable rate	2.25%