Variable Interest Entities (Summary of application of the measurement alternative results in the company's earnings from consolidated vie subsequent to initial consolidation) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Oct. 31, 2020	Jul. 31, 2020	Apr. 30, 2020	Jan. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Apr. 30, 2019	Jan. 31, 2019	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2018
Economic interests in Consolidated Securitized CLO Entities [Abstract]
Management fees	$ 451,081	$ 420,819	$ 405,911	$ 452,554	$ 433,740	$ 431,235	$ 411,861	$ 406,416	$ 1,730,365	$ 1,683,252	$ 1,692,422
Total economic interests									(117,231)	9,090	11,373
Consolidated Securitized CLO Entities [Member]
Economic interests in Consolidated Securitized CLO Entities [Abstract]
Distributions received and gains (losses) on the senior and subordinated interests held by the company									(24,939)	3,266	(2,319)
Management fees									6,362	5,838	787
Total economic interests									$ (18,577)	$ 9,104	$ (1,532)