EARNINGS PER COMMON SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended	3 Months Ended		5 Months Ended	9 Months Ended
	Jan. 15, 2016	Aug. 20, 2015	Aug. 30, 2015	Sep. 30, 2017	Sep. 30, 2016	Jan. 15, 2016	Sep. 30, 2017	Sep. 30, 2016
Basic earnings (loss) per common share
Net income (loss)				$ (457,084)	$ 186,613		$ (341,541)	$ 364,460
Less: preferred share dividends				10,656	9,969		36,154	29,906
Net income (loss) available to common shareholders				$ (467,740)	$ 176,644		$ (377,695)	$ 334,554
Weighted average number of common shares outstanding - basic (in shares)				83,305,000	89,621,000		84,479,000	91,852,000
Basic earnings (loss) per common share (in usd per share)				$ (5.61)	$ 1.97		$ (4.47)	$ 3.64
Diluted earnings (loss) per common share
Net income (loss) available to common shareholders				$ (467,740)	$ 176,644		$ (377,695)	$ 334,554
Weighted average number of common shares outstanding - basic (in shares)				83,305,000	89,621,000		84,479,000	91,852,000
Share based compensation plans (in shares)				0	730,000		0	727,000
Weighted average number of common shares outstanding - diluted (in shares)				83,305,000	90,351,000		84,479,000	92,579,000
Diluted earnings (loss) per common share (in usd per share)				$ (5.61)	$ 1.96		$ (4.47)	$ 3.61
Anti-dilutive shares excluded from the dilutive computation (in shares)				425,000	0		712,000	226,000
August 17, 2015 ASR agreement [Member]
Diluted earnings (loss) per common share
Shares repurchased (in shares)	1,358,380.00	4,149,378	4,149,378			5,507,758