Consolidated K-Series - Condensed Statement of Operations of Consolidated K-Series (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Condensed Income Statements, Captions [Line Items]
Interest expense	$ 147,631	$ 90,646	$ 410,976	$ 270,009
NET INTEREST INCOME	31,971	19,603	83,866	56,854
Unrealized gains, net	11,112	14,094	13,898	57,518
NET INCOME ATTRIBUTABLE TO COMPANY	41,379	33,973	108,254	93,285
Consolidated K-Series
Condensed Income Statements, Captions [Line Items]
Interest income	139,818	86,458	384,743	257,179
Interest expense	120,329	75,145	332,041	224,310
NET INTEREST INCOME	19,489	11,313	52,702	32,869
Unrealized gains, net	7,630	12,303	22,247	31,867
NET INCOME ATTRIBUTABLE TO COMPANY	$ 27,119	$ 23,616	$ 74,949	$ 64,736