Assets and Liabilities Held For Sale - Schedule of Major Classes of Assets and Liabilities Classified as Held-for-Sale (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accrued commissions and other receivables, net	$ 338,313	$ 739,009
Cash segregated under regulatory requirements	36,365	257,031
Goodwill	487,434	556,211
Other intangible assets, net	219,291	287,157
Other assets	461,379	480,418
Cash and cash equivalents	420,302	593,646
Loans, forgivable loans and other receivables from employees and partners, net	370,800	408,142
Fixed assets, net	204,531	214,782
Assets held for sale	1,048,859	0
Accounts payable, accrued and other liabilities	652,366	1,363,919
Accrued compensation	187,166	220,726
Liabilities held for sale	850,112	$ 0
Disposal Group, Held-for-sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Other intangible assets, net	56,031
Fixed assets, net	8,606
Disposal Group, Held-for-sale, Not Discontinued Operations | Brokerage Insurance
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Accrued commissions and other receivables, net	561,074
Cash segregated under regulatory requirements	274,107
Goodwill	69,725
Other intangible assets, net	56,031
Other assets	33,290
Cash and cash equivalents	28,571
Loans, forgivable loans and other receivables from employees and partners, net	14,496
Fixed assets, net	8,606
Other	2,959
Assets held for sale	1,048,859
Accounts payable, accrued and other liabilities	839,872
Accrued compensation	10,233
Other	7
Liabilities held for sale	$ 850,112