LONG-TERM DEBT (Details) (Medium-term Notes [Member], USD $)	1 Months Ended
	Feb. 28, 2012 Series Due 2027, 7.7 Percent [Member]	Mar. 31, 2013 Series Due 2027, 7.7 Percent [Member]	Dec. 31, 2011 Series Due 2027, 7.7 Percent [Member]	Apr. 30, 2012 Series Due 2032, 3.74 Percent [Member]
Debt Instrument [Line Items]
Approved borrowing capacity			$ 200,000,000.0
Remaining balance available under note program		80,000,000
Debt called	35,000,000.0
Stated interest rate	7.70%			3.74%
Premium in addition to par for called debt	2.00%
Debt issued				$ 35,000,000