PROPERTY: (Details) (USD $)	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property
Total property	$ 10,986,700,000	$ 9,412,300,000
Accumulated depreciation, amortization and depletion	(4,510,500,000)	(4,255,600,000)
Total property, net	6,476,168,000	5,156,731,000	4,429,900,000
Depreciation and depletion expense	393,600,000	323,600,000	286,000,000
Buildings and equipment
Property
Total property	8,107,200,000	7,497,300,000
Construction in progress
Property
Total property	2,567,000,000	1,617,600,000
Mine development
Property
Total property	250,700,000	250,700,000
Total property, net	36,200,000	37,900,000
Land, other than mineral
Property
Total property	$ 61,800,000	$ 46,700,000

The cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land) that has been recognized in the income statement.

+ References+ Details

Gross amount of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References+ Details

- Definition

Amount, net of accumulated depreciation, depletion and amortization, of long-lived physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References+ Details