Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Tradeweb Markets LLC	Equity Incentive Plan Class A common stock	Refinitiv Transaction	Members' Capital	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Retained Earnings	Non-Controlling Interests	Class A common stock	Class B common stock	Class C common stock	Class D common stock	Total
Members' capital beginning of period at Dec. 31, 2017				$ 999,735		$ (13,267)							$ 986,468
Comprehensive income:
Capital distributions				(25,000)									(25,000)
Net income				45,308									45,308
Foreign currency translation adjustments						1,928							1,928
Members' capital end of period at Mar. 31, 2018				1,020,043		(11,339)							1,008,704
Members' capital beginning of period at Dec. 31, 2017				999,735		(13,267)							986,468
Comprehensive income:
Net income													130,160
Total comprehensive income	$ 127,096
Vesting of contingent consideration			$ 150,495
Members' capital end of period at Sep. 30, 2018				1,141,496		(16,331)							$ 1,125,165
Comprehensive income:
Financial Designation, Predecessor and Successor [Fixed List]													Predecessor
Members' capital beginning of period at Mar. 31, 2018				1,020,043		(11,339)							$ 1,008,704
Comprehensive income:
Capital distributions				(55,000)									(55,000)
Net income				38,897									38,897
Foreign currency translation adjustments						(3,986)							(3,986)
Members' capital end of period at Jun. 30, 2018				1,003,940		(15,325)							988,615
Comprehensive income:
Adjustment to Class C Shares and Class P© shares in mezzanine capital				456									456
Capital distributions				(59,350)									(59,350)
Net income				45,955									45,955
Foreign currency translation adjustments						(1,006)							(1,006)
Total comprehensive income	44,949			45,955		(1,006)							44,949
Vesting of contingent consideration				150,495									150,495
Members' capital end of period at Sep. 30, 2018				1,141,496		(16,331)							$ 1,125,165
Comprehensive income:
Financial Designation, Predecessor and Successor [Fixed List]													Predecessor
Members' capital beginning of period at Dec. 31, 2018				4,573,200
Equity at beginning of period at Dec. 31, 2018						(866)							$ 4,572,334
Comprehensive income:
Adjustment to Class C Shares and Class P© shares in mezzanine capital				(2,369)									(2,369)
Capital distributions				(20,000)									(20,000)
Stock-based compensation				4,674									4,674
Net income				42,352									42,352
Foreign currency translation adjustments						988							988
Members' capital end of period at Mar. 31, 2019				4,597,857
Equity at end of period at Mar. 31, 2019						122							4,597,979
Members' capital beginning of period at Dec. 31, 2018				4,573,200
Equity at beginning of period at Dec. 31, 2018						(866)							4,572,334
Comprehensive income:
Net income													115,746
Total comprehensive income	$ 43,340												40,464
Equity at end of period at Sep. 30, 2019					$ 2,855,885	(1,854)	$ 19,570	$ 1,613,633		$ 1		$ 1	4,487,236
Equity at end of period (in shares) at Sep. 30, 2019									46,009,753	96,933,192	10,006,269	69,282,736
Members' capital beginning of period at Mar. 31, 2019				4,597,857
Equity at beginning of period at Mar. 31, 2019						122							4,597,979
Comprehensive income:
Effect of the reorganization transactions				(4,497,857)	4,521,132								23,275
Issuance of common stock					(15,856)					$ 1		$ 1	(15,854)
Issuance of common stock (in shares)									46,000,000	96,933,192	10,006,269	69,282,736
Tax receivable agreement liability and deferred taxes arising from the reorganization transactions and IPO					(78,232)								(78,232)
Allocation of equity to non-controlling interests					(1,607,529)			1,607,529
Distributions to non-controlling interests								(11,909)					(11,909)
Dividends ($0.08 per share)							(11,435)						(11,435)
Capital distributions				$ (100,000)									(100,000)
Share-based compensation expense under the PRSU Plan					6,763								6,763
Share-based compensation expense under the Option Plan					20,403								20,403
Net income							12,828	11,988					24,816
Foreign currency translation adjustments						(647)		(359)					(1,006)
Equity at end of period at Jun. 30, 2019					2,846,681	(525)	1,393	1,607,249		$ 1		$ 1	4,454,800
Equity at end of period (in shares) at Jun. 30, 2019									46,000,000	96,933,192	10,006,269	69,282,736
Comprehensive income:
Issuance of common stock (in shares)		9,753
Adjustments to non-controlling interest					73			(73)
Distributions to non-controlling interests								(11,772)					(11,772)
Dividends ($0.08 per share)							(11,435)						(11,435)
Share-based compensation expense under the PRSU Plan					7,136								7,136
Share-based compensation expense under the Option Plan					1,995								1,995
Net income							29,612	18,966					48,578
Foreign currency translation adjustments						(1,329)		(737)					(2,066)
Total comprehensive income													28,283
Equity at end of period at Sep. 30, 2019					$ 2,855,885	$ (1,854)	$ 19,570	$ 1,613,633		$ 1		$ 1	$ 4,487,236
Equity at end of period (in shares) at Sep. 30, 2019									46,009,753	96,933,192	10,006,269	69,282,736