DEBT (Details) (USD $)	12 Months Ended						0 Months Ended		0 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Senior Notes	Dec. 31, 2012 Senior Notes	Dec. 31, 2011 Senior Notes	Oct. 02, 2013 Senior notes maturing September 15, 2023	Dec. 31, 2013 Senior notes maturing September 15, 2023	Dec. 12, 2013 Senior notes maturing January 15, 2014	Dec. 31, 2013 Revolving line of credit	Dec. 31, 2012 Revolving line of credit	Dec. 31, 2011 Revolving line of credit
Debt
Outstanding long-term senior notes				$ 149,600,000
Issue of senior notes by public debt offering							150,000,000
Stated interest rate, payable semi-annually (as a percent)							4.875%
Proceeds from issuance of debt, net of discount and commission							148,600,000
Amount of principle redeemed									100,000,000
Estimated fair value of senior notes								150,800,000
Borrowing capacity under revolving line of credit facility										25,000,000
Maximum borrowing capacity conditional expansion										50,000,000
Term of facility										3 years
Amount outstanding on this facility										0	0	0
Average interest rate on debt (as a percent)				5.71%	6.02%	6.02%
Interest paid on outstanding debt	$ 8,095,000	$ 6,050,000	$ 6,050,000	$ 8,100,000	$ 6,000,000	$ 6,000,000