ITG Acquisition - Pro Forma Financial Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Revenue	$ 3,239,331	$ 1,517,492	$ 1,878,718
Net income (loss)	1,120,913	(103,705)	620,192
Net income (loss) available for common stockholders	$ 649,197	(58,595)	289,441
Pro Forma
Business Acquisition [Line Items]
Revenue		1,605,340	2,388,194
Net income (loss)		(94,233)	514,821
Net income (loss) available for common stockholders		$ (53,243)	$ 240,265