EARNINGS PER COMMON SHARE (DETAILS) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								5 Months Ended	12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Jan. 15, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Basic earnings per common share
Net income										$ 513,368	$ 641,631	$ 804,564
Less: amounts attributable from noncontrolling interests										0	0	(6,181)
Less: preferred share dividends										46,597	40,069	40,088
Less: loss on repurchase of preferred shares										1,309	0	0
Net income available to common shareholders	$ 130,912	$ 176,644	$ 119,491	$ 38,417	$ 134,787	$ 247,620	$ 63,349	$ 155,803		$ 465,462	$ 601,562	$ 770,657
Weighted average common shares outstanding - basic (in shares)										90,772,000	98,609,000	104,368,000
Basic earnings per common share (in dollars per share)	$ 1.50	$ 1.97	$ 1.30	$ 0.41	$ 1.40	$ 2.52	$ 0.63	$ 1.56		$ 5.13	$ 6.10	$ 7.38
Diluted earnings per common share
Net income available to common shareholders	$ 130,912	$ 176,644	$ 119,491	$ 38,417	$ 134,787	$ 247,620	$ 63,349	$ 155,803		$ 465,462	$ 601,562	$ 770,657
Weighted average common shares outstanding - basic (in shares)										90,772,000	98,609,000	104,368,000
Share-based compensation plans (in shares)										775,000	1,020,000	1,345,000
Weighted average common shares outstanding - diluted (in shares)										91,547,000	99,629,000	105,713,000
Diluted earnings per common share (in dollars per share)	$ 1.48	$ 1.96	$ 1.29	$ 0.41	$ 1.39	$ 2.50	$ 0.63	$ 1.54		$ 5.08	$ 6.04	$ 7.29
Anti-dilutive shares excluded from the dilutive computation (in shares)										170,000	165,000	282,000
Accelerated Share Repurchase Agreement August 17 2015 [Member]
Accelerated Share Repurchases [Line Items]
Shares repurchased (in shares)									5,507,758	1,358,380	4,149,378