COMMON STOCK: Common Stock, Number of Shares, Par Value and Other Disclosures (Details)					12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2012 Continuous equity program	Dec. 31, 2011 Continuous equity program	Dec. 31, 2010 Continuous equity program	Dec. 31, 2012 Dividend reinvestment and stock purchase plan	Dec. 31, 2011 Dividend reinvestment and stock purchase plan	Dec. 31, 2010 Dividend reinvestment and stock purchase plan	Dec. 31, 2012 Employee savings plan	Dec. 31, 2011 Employee savings plan	Dec. 31, 2010 Employee savings plan	Dec. 31, 2012 Long-term incentive and compensation plan	Dec. 31, 2011 Long-term incentive and compensation plan	Dec. 31, 2010 Long-term incentive and compensation plan	Dec. 31, 2012 Restricted stock plan	Dec. 31, 2011 Restricted stock plan	Dec. 31, 2010 Restricted stock plan
Common stock issued [Roll Forward]
Common Stock, Shares, Issued	50,158,486	49,964,172	49,419,452	47,925,882
Shares issued during the year					0	0	973,585	62,084	119,999	144,655	49,296	91,277	105,375	82,934	333,444	256,662	0	0	13,293
Common Stock, Shares, Issued	50,158,486	49,964,172	49,419,452	47,925,882
Shares reserved for future issuance					3,000,000			2,576,723			3,567,954			1,618,260			256,154