STOCKHOLDERS' EQUITY: - Repurchase (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended			3 Months Ended		12 Months Ended			60 Months Ended	105 Months Ended
	Sep. 30, 2016	Aug. 31, 2016	Jan. 31, 2016	Sep. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2016	Dec. 31, 2008
SCC share repurchase program:
Amount authorized for share repurchase program	$ 3,000.0			$ 3,000.0						$ 3,000.0	$ 500.0
Total Number of Shares Purchased	587,601	115,000	2,235,200	702,601	2,235,200	36,689,052	22,711,428	10,245,000	46,914,486	119,497,767
Average Price Paid per Share (in dollars per share)	$ 25.55	$ 25.88	$ 24.05	$ 25.61	$ 24.05	$ 27.38	$ 30.06	$ 27.47	$ 18.72	$ 24.42
Total Number of Shares Purchased as Part of Publicly Announced Plan	119,497,767	118,910,166	118,795,166	119,497,767		116,559,966	79,870,914	57,159,486	46,914,486	119,497,767
Maximum Number of Shares that May Yet Be Purchased Under the Plan @ $26.30	3,103,930			3,103,930						3,103,930
Total Cost	$ 15.0	$ 3.0	$ 53.7	$ 18.0	$ 53.7	$ 1,004.4	$ 682.8	$ 281.4	$ 878.1	$ 2,918.4
Percentage of ownership interest held by the parent company	88.90%			88.90%						88.90%