SUBSEQUENT EVENTS - Dividend Declaration (Details) - $ / shares		12 Months Ended
	Feb. 05, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Subsequent Event
Common stock dividends declared (in dollars per share)		$ 1.73	$ 1.67	$ 1.60
Dividend Declared | Subsequent Event
Subsequent Event
Common stock dividends declared (in dollars per share)	$ 0.45
Dividend Declared | Series A Preferred Stock | Subsequent Event
Subsequent Event
Preferred stock dividends declared (in dollars per share)	$ 0.4453125