SHAREHOLDERS' EQUITY (DETAILS 4) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended						2 Months Ended	12 Months Ended
	Jan. 27, 2016	Jan. 31, 2017	Nov. 30, 2016	May 31, 2013	Apr. 30, 2012	Mar. 31, 2012	Nov. 30, 2005	Nov. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Aggregate cash payment to acquire preferred shares									$ 51,769	$ 0	$ 0
Loss on repurchase of preferred shares									1,309	0	$ 0
Preferred shares, aggregate liquidation value outstanding									$ 1,126,074	$ 627,843
Series B 7.50% Preferred Shares [Member]
Class of Stock [Line Items]
Preferred shares, aggregate liquidation value issued							$ 250,000
Preferred shares, dividend rate									7.50%
Preferred shares, par value per share									$ 0.0125
Preferred shares, liquidation preference per share									100.00
Preferred shares, redemption price per share									$ 100.00
Preferred shares, purchase price per share					$ 102.81
Preferred shares, number of shares redeemed	28,430				2,471,570
Aggregate cash payment to acquire preferred shares					$ 254,000
Loss on repurchase of preferred shares					$ 9,000
Preferred shares, dividend declared per share										$ 6.8125	$ 7.50
Preferred shares, dividends paid per share										7.50	7.50
Preferred shares, aggregate redemption price	$ 3,000
Series C 6.875% Preferred Shares [Member]
Class of Stock [Line Items]
Preferred shares, aggregate liquidation value issued						$ 400,000
Preferred shares, dividend rate									6.875%
Preferred shares, par value per share									$ 0.0125
Preferred shares, liquidation preference per share									25.00
Preferred shares, redemption price per share									25.00
Preferred shares, purchase price per share			$ 25.67					$ 25.67
Preferred shares, number of shares redeemed								1,957,045
Aggregate cash payment to acquire preferred shares								$ 50,000
Loss on repurchase of preferred shares								$ 1,000
Preferred shares, dividend declared per share									1.7188	1.7188	1.7188
Preferred shares, dividends paid per share									$ 1.7188	1.7188	1.7188
Preferred shares, number of shares outstanding			14,042,955					14,042,955
Preferred shares, aggregate liquidation value outstanding			$ 351,000					$ 351,000
Series D 5.50% Preferred Shares [Member]
Class of Stock [Line Items]
Preferred shares, aggregate liquidation value issued				$ 225,000
Preferred shares, dividend rate									5.50%
Preferred shares, par value per share									$ 0.0125
Preferred shares, liquidation preference per share									25.00
Preferred shares, redemption price per share									25.00
Preferred shares, dividend declared per share									1.3750	1.3750	1.3750
Preferred shares, dividends paid per share									1.3750	$ 1.3750	$ 1.3750
Series E 5.50% Preferred Shares [Member]
Class of Stock [Line Items]
Preferred shares, aggregate liquidation value issued			$ 550,000
Preferred shares, dividend rate			5.50%
Preferred shares, par value per share			$ 0.0125					$ 0.0125
Preferred shares, liquidation preference per share			2,500.00					2,500.00
Preferred shares, redemption price per share			$ 2,500.00					$ 2,500.00
Preferred shares, dividend declared per share									$ 34.3750
Subsequent Event [Member] | Series E 5.50% Preferred Shares [Member]
Class of Stock [Line Items]
Preferred shares, dividends paid per share		$ 0.3438