Long-Term Debt - Narrative (Details) (USD $)			12 Months Ended		12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 5.50% Senior Notes Due On November 1, 2013 [Member]	Oct. 20, 2003 5.50% Senior Notes Due On November 1, 2013 [Member]	Dec. 31, 2013 Six Point Zero Percent Senior Notes Due On June Fifteen Two Thousand And Seventeen [Member]	May 08, 2013 Six Point Zero Percent Senior Notes Due On June Fifteen Two Thousand And Seventeen [Member]	Dec. 31, 2013 Miles Kimball [Member]	Dec. 31, 2012 Miles Kimball [Member]
Debt Instrument [Line Items]
Note issuance date			Oct. 20, 2003		May 10, 2013
Senior notes issued				$ 100,000,000	$ 50,000,000
Interest rate of Senior Notes				5.50%		6.00%
Maturity date of long-term debt outstanding			Nov. 01, 2013		Jun. 01, 2017
Discount amount, over the life of the notes				200,000
Payment for notes repurcahse			73,700,000
Notes outstanding, amount			1,200,000
Long-term debt outstanding							5,500,000	6,200,000
Long-term debt fixed interest rate							7.89%
Total long-term debt	56,278,000	78,190,000
Amount available under uncommitted bank facility to be used for letters of credit	2,400,000
Letters of credit outstanding, amount	$ 1,100,000