COMMON STOCK Stock Issuance (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
September 2016 Common Stock Issuance [Member]
Class of Stock [Line Items]
Stock Issued During Period, Shares, New Issues	9,085,000
Sale of Stock, Price Per Share	$ 61.51
Proceeds from Issuance of Common Stock	$ 558.5
March 2016 Common Stock Issuance [Member]
Class of Stock [Line Items]
Stock Issued During Period, Shares, New Issues	5,922,500
Sale of Stock, Price Per Share	$ 50.11
March 2015 Common Stock Issuance
Class of Stock [Line Items]
Stock Issued During Period, Shares, New Issues		4,002,000
Sale of Stock, Price Per Share		$ 50.73
Proceeds from Issuance of Common Stock	$ 296.6	$ 202.9