Note 16 - Preferred Stock, Common Stock and Convertible Unit Transactions (Tables)

12 Months Ended

Dec. 31, 2015

Outstanding Preferred Stock [Member]

Note 16 - Preferred Stock, Common Stock and Convertible Unit Transactions (Tables) [Line Items]

Schedule of Stockholders Equity [Table Text Block]

As of December 31, 2015
Series of Preferred Stock	Shares Authorized		Shares Issued and Outstanding		Liquidation Preference		Dividend Rate			Annual Dividend per Depositary Share		Par Value
Series I		18,400		16,000	$	400,000		6.00	%	$	1.50000	$	1.00
Series J		9,000		9,000		225,000		5.50	%	$	1.37500	$	1.00
Series K		8,050		7,000		175,000		5.625	%	$	1.40625	$	1.00
		35,450		32,000	$	800,000

As of December 31, 2014
Series of  Preferred Stock	Shares Authorized		Shares Issued and Outstanding		Liquidation Preference		Dividend Rate			Annual Dividend per Depositary Share		Par Value
Series H		70,000		70,000	$	175,000		6.90	%	$	1.72500	$	1.00
Series I		18,400		16,000		400,000		6.00	%	$	1.50000	$	1.00
Series J		9,000		9,000		225,000		5.50	%	$	1.37500	$	1.00
Series K		8,050		7,000		175,000		5.625	%	$	1.40625	$	1.00
		105,450		102,000	$	975,000

Preferred Stock Issued [Member]

Note 16 - Preferred Stock, Common Stock and Convertible Unit Transactions (Tables) [Line Items]

Schedule of Stockholders Equity [Table Text Block]

Series of  Preferred Stock	Date Issued	Depositary Shares Issued		Fractional Interest per Share	Net Proceeds, After Expenses (in millions)		Offering/ Redemption Price		Optional Redemption Date
Series I (2)	3/20/2012		16,000,000	1/1000	$	387.2	$	25.00	3/20/2017
Series J (3)	7/25/2012		9,000,000	1/1000	$	217.8	$	25.00	7/25/2017
Series K (4)	12/7/2012		7,000,000	1/1000	$	169.1	$	25.00	12/7/2017

Series of  Preferred Stock	Date Issued	Depositary Shares Issued		Fractional Interest per Share	Net Proceeds, After Expenses (in millions)		Offering/ Redemption Price		Optional Redemption Date
Series H (1)	8/30/2010		7,000,000	1/100	$	169.2	$	25.00	8/30/2015
Series I (2)	3/20/2012		16,000,000	1/1000	$	387.2	$	25.00	3/20/2017
Series J (3)	7/25/2012		9,000,000	1/1000	$	217.8	$	25.00	7/25/2017
Series K (4)	12/7/2012		7,000,000	1/1000	$	169.1	$	25.00	12/7/2017

Preferred Stock Redeemed [Member]

Note 16 - Preferred Stock, Common Stock and Convertible Unit Transactions (Tables) [Line Items]

Schedule of Stockholders Equity [Table Text Block]

Series of Preferred Stock	Date Issued	Depositary Shares Issued		Redemption Amount (in millions)		Offering/ Redemption Price		Optional Redemption Date	Actual Redemption Date
Series H (1)	8/30/2010		7,000,000	$	175.0	$	25.00	8/30/2015	11/25/2015