Fair Value Measurements - Estimated Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Financial assets:
Held to maturity securities	$ 876,531	$ 276,296
Loans held for investment, net	7,835,321	7,788,552
Broker-dealer and clearing organization receivables	1,049,830	1,672,946
Financial liabilities:
Broker-dealer and clearing organization payables	934,818	1,477,300
Carrying Amount
Financial assets:
Cash and cash equivalents	1,783,935	2,823,523
Assets segregated for regulatory purposes	120,816	221,740
Securities purchased under agreements to resell	139,929	118,262
Held to maturity securities	920,583	267,684
Loans held for sale	119,197	95,599
Loans held for investment, net	7,826,294	7,788,552
Broker-dealer and clearing organization receivables	1,049,830	1,672,946
Other assets	70,069	73,041
Financial liabilities:
Deposits	11,920,786	12,818,077
Broker-dealer and clearing organization payables	934,818	1,477,300
Short-term borrowings	822,649	859,444
Debt	389,722	387,904
Other liabilities	3,895	3,944
Estimate of Fair Value
Financial assets:
Cash and cash equivalents	1,783,935	2,823,523
Assets segregated for regulatory purposes	120,816	221,740
Securities purchased under agreements to resell	139,929	118,262
Held to maturity securities	876,531	276,296
Loans held for sale	119,197	95,599
Loans held for investment, net	7,728,445	7,999,925
Broker-dealer and clearing organization receivables	1,049,830	1,672,946
Other assets	70,069	73,041
Financial liabilities:
Deposits	11,907,658	12,821,138
Broker-dealer and clearing organization payables	934,818	1,477,300
Short-term borrowings	822,649	859,444
Debt	389,722	387,904
Other liabilities	3,895	3,944
Estimate of Fair Value \| Level 1
Financial assets:
Cash and cash equivalents	1,783,935	2,823,523
Assets segregated for regulatory purposes	120,816	221,740
Estimate of Fair Value \| Level 2
Financial assets:
Securities purchased under agreements to resell	139,929	118,262
Held to maturity securities	876,531	276,296
Loans held for sale	119,197	95,599
Loans held for investment, net	463,004	733,193
Broker-dealer and clearing organization receivables	1,049,830	1,672,946
Other assets	68,397	71,290
Financial liabilities:
Deposits	11,907,658	12,821,138
Broker-dealer and clearing organization payables	934,818	1,477,300
Short-term borrowings	822,649	859,444
Debt	389,722	387,904
Other liabilities	3,895	3,944
Estimate of Fair Value \| Level 3
Financial assets:
Loans held for investment, net	7,265,441	7,266,732
Other assets	$ 1,672	$ 1,751

Fair value portion of assets segregated for regulatory purposes.

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Amount payable to other broker-dealer and clearing organization, including, but not limited to, security failed-to-receive, deposit received for security loaned, open transaction, and floor-brokerage payable.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

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Fair value portion of federal funds sold and securities borrowed or purchased under agreements to resell.

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Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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Amortized cost, after allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

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Fair value portion of other assets.

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Fair value portion of other liabilities.

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Amount receivable from broker-dealers and clearing organizations, including, but not limited to, securities failed-to-deliver, certain deposits for securities borrowed, open transactions, good faith and margin deposits, commissions and floor brokerage receivables.

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