Schedule I - Parent Company Only Financial Statements - Statements of Cash Flows (Detail) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Dec. 31, 2023	Jun. 30, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss) available to common stockholders			$ 123,228	$ 38,775	$ 58,867
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Deferred tax (benefit) expense			(69,754)	(60,556)	(14,628)
Decrease (increase) in operating assets:
Receivables from related parties			(3,890)	(1,380)	3,621
Other assets			(10,674)	19,803	(8,469)
(Decrease) increase in operating liabilities:
Accounts payable, accrued and other liabilities			(8,900)	(34,595)	(37,841)
CASH FLOWS FROM INVESTING ACTIVITIES:
Loan to related parties			180,000	0	0
Repayment of loan to related parties			180,000	0	0
Net cash provided by (used in) investing activities			(96,994)	(90,707)	(53,330)
CASH FLOWS FROM FINANCING ACTIVITIES:
Dividends to stockholders			(34,165)	(17,381)	(14,859)
Repurchase of Class A common stock			(262,211)	(114,580)	(103,888)
Redemption of equity awards			(138,894)	(117,867)	(76,219)
Net increase (decrease) in cash and cash equivalents			60,377	170,886	(64,789)
Cash and cash equivalents, and Cash segregated under regulatory requirements at beginning of period		$ 502,010	672,896	502,010	566,799
Cash and cash equivalents, and Cash segregated under regulatory requirements at end of period	$ 672,896		733,273	672,896	502,010
Supplemental cash information:
Cash paid during the period for interest			88,392	80,664	53,655
Supplemental non-cash information:
Issuance of Class A common stock upon exchange of limited partnership interests			0	45,868	34,889
Issuance of Class A and contingent Class A common stock and limited partnership interests for acquisitions			8,520	7,275	2,710
Parent Company
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss) available to common stockholders	36,991	(726)	126,988		48,712
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Amortization of deferred financing costs	774	1,461	1,166		2,801
Equity (income) loss of subsidiaries	(36,991)	726	(126,988)		(48,712)
Deferred tax (benefit) expense	(51,527)	0	(67,500)		(20,341)
Decrease (increase) in operating assets:
Investments in subsidiaries	207,931	(552)	384,934		55,706
Receivables from related parties	(12,744)	253	(498)		878
Notes receivable from related party	(1,124,589)	(348,040)	(196,192)		(2,801)
Other assets	(87,613)	3,836	(48,445)		(1,052)
(Decrease) increase in operating liabilities:
Accounts payable, accrued and other liabilities	20,191	3,568	(6,517)		(5,750)
Net cash provided by (used in) operating activities	(1,047,577)	(339,474)	66,948		29,441
CASH FLOWS FROM INVESTING ACTIVITIES:
Loan to related parties	0	0	180,000		0
Repayment of loan to related parties	0	0	180,000		0
Net cash provided by (used in) investing activities	0	0	0		0
CASH FLOWS FROM FINANCING ACTIVITIES:
Dividends to stockholders	(9,360)	(7,558)	(33,800)		(14,859)
Repurchase of Class A common stock	(66,778)	(46,481)	(262,211)		(103,888)
Issuance of senior notes, net of deferred issuance costs	884,781	346,579	494,989		0
Redemption of equity awards	(155)	(1,043)	0		0
Repayments of senior notes	0	0	(255,526)		0
Unsecured revolving credit agreement borrowings	239,033	0	470,564		0
Unsecured revolving credit agreement repayments	0	0	(515,000)		0
Repayment of short-term borrowings from related parties	0	0	(275,000)		0
Issuance of short term borrowings from related parties	0	0	275,000		0
Distributions from subsidiaries	0	47,861	33,800		89,234
Proceeds from dividend reinvestment plan	85	84	277		90
Net cash provided by (used in) financing activities	1,047,606	339,442	(66,907)		(29,423)
Net increase (decrease) in cash and cash equivalents	29	(32)	41		18
Cash and cash equivalents, and Cash segregated under regulatory requirements at beginning of period	17	49	29	49	31
Cash and cash equivalents, and Cash segregated under regulatory requirements at end of period	29	17	70	$ 29	49
Supplemental cash information:
Cash paid (refund) during the period for taxes	0	9,581	(5)		5,269
Cash paid during the period for interest	10,702	26,404	78,448		49,375
Supplemental non-cash information:
Issuance of Class A common stock upon exchange of limited partnership interests	0	45,868	0		34,889
Issuance of Class A and contingent Class A common stock and limited partnership interests for acquisitions	$ 4,514	$ 2,761	$ 8,519		$ 2,710