CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Interest receivable - Consolidated Trusts amount	$ 156,194	$ 155,278
Accrued interest payable - Consolidated Trusts amount	$ 88,506	$ 75,402
Series A Preferred Stock [Member]
Preferred stock, par value	$ 25	$ 25
Preferred stock, shares authorized	2,400,000	2,400,000
Preferred Stock, Shares Issued	2,400,000	2,400,000
Preferred Stock, Shares Outstanding	2,400,000	2,400,000
Series B Preferred Stock [Member]
Preferred stock, par value	$ 25	$ 25
Preferred stock, shares authorized	3,000,000	3,000,000
Preferred Stock, Shares Issued	3,000,000	3,000,000
Preferred Stock, Shares Outstanding	3,000,000	3,000,000
Series C Preferred Stock [Member]
Preferred stock, par value	$ 25	$ 25
Preferred stock, shares authorized	3,000,000	3,000,000
Preferred Stock, Shares Issued	3,000,000	3,000,000
Preferred Stock, Shares Outstanding	3,000,000	3,000,000
Common Class A, Voting [Member]
Common stock, par value	$ 1	$ 1
Common stock, shares outstanding	1,030,780	1,030,780
Common Class B, Voting [Member]
Common stock, par value	$ 1	$ 1
Common stock, shares outstanding	500,301	500,301
Common Class C, Non-Voting [Member]
Common stock, par value	$ 1	$ 1
Common stock, shares outstanding	9,136,194	9,087,670
Variable Interest Entity, Primary Beneficiary [Member]
Interest receivable - Consolidated Trusts amount	$ 17,019	$ 17,373
Accrued interest payable - Consolidated Trusts amount	$ 14,559	$ 14,631