CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Interest receivable - Consolidated Trusts amount	$ 184,693	$ 180,080
Accrued interest payable - Consolidated Trusts amount	$ 108,129	$ 96,743
Series A Preferred Stock [Member]
Preferred stock, par value (in dollars per share)	$ 25	$ 25
Preferred stock, shares authorized (in shares)	2,400,000	2,400,000
Preferred stock, shares issued (in shares)	2,400,000	2,400,000
Preferred stock, shares outstanding (in shares)	2,400,000	2,400,000
Series B Preferred Stock [Member]
Preferred stock, par value (in dollars per share)	$ 25	$ 25
Preferred stock, shares authorized (in shares)	3,000,000	3,000,000
Preferred stock, shares issued (in shares)	3,000,000	3,000,000
Preferred stock, shares outstanding (in shares)	3,000,000	3,000,000
Preferred stock, redemption amount	$ 75,000	$ 75,000
Series C Preferred Stock [Member]
Preferred stock, par value (in dollars per share)	$ 25	$ 25
Preferred stock, shares authorized (in shares)	3,000,000	3,000,000
Preferred stock, shares issued (in shares)	3,000,000	3,000,000
Preferred stock, shares outstanding (in shares)	3,000,000	3,000,000
Series D Preferred Stock [Member]
Preferred stock, par value (in dollars per share)	$ 25	$ 25
Preferred stock, shares authorized (in shares)	4,000,000	4,000,000
Preferred stock, shares issued (in shares)	4,000,000	4,000,000
Preferred stock, shares outstanding (in shares)	4,000,000	4,000,000
Common Class A, Voting [Member]
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares outstanding (in shares)	1,030,780	1,030,780
Common Class B, Voting [Member]
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares outstanding (in shares)	500,301	500,301
Common Class C, Non-Voting [Member]
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares outstanding (in shares)	9,168,893	9,137,550
Variable Interest Entity, Primary Beneficiary [Member]
Interest receivable - Consolidated Trusts amount	$ 18,811	$ 19,783
Accrued interest payable - Consolidated Trusts amount	$ 16,077	$ 17,125

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