Note 15 - Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2019

Notes Tables

Schedule of Stockholders Equity [Table Text Block]

As of September 30, 2019
Class of Preferred Stock	Shares Authorized		Shares Issued and Outstanding		Liquidation Preference (in thousands)		Dividend Rate	Annual Dividend per Depositary Share		Par Value		Optional Redemption Date
Class J		9,000		9,000	$	225,000	5.500%	$	1.37500	$	1.00	7/25/2017
Class L		10,350		9,000		225,000	5.125%	$	1.28125	$	1.00	8/16/2022
Class M		10,580		10,580		264,500	5.250%	$	1.31250	$	1.00	12/20/2022
				28,580	$	714,500

As of December 31, 2018
Class of Preferred Stock	Shares Authorized		Shares Issued and Outstanding		Liquidation Preference (in thousands)		Dividend Rate	Annual Dividend per Depositary Share		Par Value		Optional Redemption Date
Class I		18,400		7,000	$	175,000	6.000%	$	1.50000	$	1.00	3/20/2017
Class J		9,000		9,000		225,000	5.500%	$	1.37500	$	1.00	7/25/2017
Class K		8,050		7,000		175,000	5.625%	$	1.40625	$	1.00	12/7/2017
Class L		10,350		9,000		225,000	5.125%	$	1.28125	$	1.00	8/16/2022
Class M		10,580		10,580		264,500	5.250%	$	1.31250	$	1.00	12/20/2022
				42,580	$	1,064,500

Dividends Declared [Table Text Block]

	Three Months Ended September 30,				Nine months Ended September 30,
	2019		2018		2019		2018
Common Shares	$	0.28000	$	0.28000	$	0.84000	$	0.84000
Class I Depositary Shares	$	0.24583	$	0.37500	$	0.99583	$	1.12500
Class J Depositary Shares	$	0.34375	$	0.34375	$	1.03125	$	1.03125
Class K Depositary Shares	$	0.23047	$	0.35156	$	0.93359	$	1.05468
Class L Depositary Shares	$	0.32031	$	0.32031	$	0.96093	$	0.96093
Class M Depositary Shares	$	0.32813	$	0.32813	$	0.98439	$	0.98439

Preferred Stock Redeemed [Member]

Notes Tables

Schedule of Stockholders Equity [Table Text Block]

Class of Preferred Stock	Redemption Date	Depositary Shares Redeemed	Redemption Price		Redemption Amount (in millions)		Redemption Charges (1) (in millions)
Class I	9/14/2019	7,000,000	$	25.00	$	175.0	$	5.5
Class K	9/14/2019	7,000,000	$	25.00	$	175.0	$	5.9