Schedule I - Parent Company Only Financial Statements - Statements of Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss) available to common stockholders	$ 58,867	$ 153,488	$ 50,918
Adjustments to reconcile net income to net cash used in operating activities:
Deferred tax (benefit) expense	(14,628)	(11,947)	(16,549)
Decrease (increase) in operating assets:
Receivables from related parties	3,621	8,377	5,465
Other assets	(8,469)	1,543	(20,074)
(Decrease) increase in operating liabilities:
Accounts payable, accrued and other liabilities	(37,841)	106,919	57,949
CASH FLOWS FROM INVESTING ACTIVITIES:
Net cash provided by (used in) investing activities	0	0	0
CASH FLOWS FROM FINANCING ACTIVITIES:
Dividends to stockholders	(14,859)	(15,098)	(60,440)
Repurchase of Class A common stock	(103,888)	(365,398)	(6)
Redemption of limited partnership interests	(76,219)	(110,565)	(47,613)
Net increase (decrease) in cash and cash equivalents	(64,789)	(286,607)	212,568
Cash and cash equivalents, and Cash segregated under regulatory requirements at beginning of period	566,799	853,406	640,838
Cash and cash equivalents, and Cash segregated under regulatory requirements at end of period	502,010	566,799	853,406
Supplemental cash information:
Cash paid during the period for interest	53,655	66,450	69,572
Supplemental non-cash information:
Issuance of Class A common stock upon exchange of limited partnership interests	34,889	157,547	11,388
Issuance Of Class Common Stock And Limited Partnership Interests For Acquisitions	2,710	1,160	1,578
Parent Company
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss) available to common stockholders	48,712	124,007	45,062
Adjustments to reconcile net income to net cash used in operating activities:
Amortization of deferred financing costs	2,801	3,592	4,188
Equity (income) loss of subsidiaries	(48,712)	(114,971)	(38,030)
Deferred tax (benefit) expense	(20,341)	(6,404)	(13,585)
Decrease (increase) in operating assets:
Investments in subsidiaries	55,706	335,295	(11,480)
Receivables from related parties	878	(7,280)	1,241
Note receivable from related party	(2,801)	251,312	(187,069)
Other assets	(1,052)	1,769	887
(Decrease) increase in operating liabilities:
Accounts payable, accrued and other liabilities	(5,750)	(21,459)	14,295
Net cash provided by (used in) operating activities	29,441	565,861	(184,491)
CASH FLOWS FROM FINANCING ACTIVITIES:
Dividends to stockholders	(14,859)	(15,098)	(60,440)
Repurchase of Class A common stock	(103,888)	(365,398)	(5)
Issuance of senior notes, net of deferred issuance costs	0	0	294,396
Repayments of senior notes	0	(256,032)	(43,968)
Unsecured revolving credit agreement borrows	0	300,000	230,000
Unsecured revolving credit agreement repayments	0	(300,000)	(300,000)
Distributions from subsidiaries	89,234	70,602	61,972
Proceeds from issuance of Class A common stock, net of costs	90	72	2,516
Net cash provided by (used in) financing activities	(29,423)	(565,854)	184,471
Net increase (decrease) in cash and cash equivalents	18	7	(20)
Cash and cash equivalents, and Cash segregated under regulatory requirements at beginning of period	31	24	44
Cash and cash equivalents, and Cash segregated under regulatory requirements at end of period	49	31	24
Supplemental cash information:
Cash paid (refund) during the period for taxes	5,269	(157)	(5,919)
Cash paid during the period for interest	49,375	59,018	60,594
Supplemental non-cash information:
Issuance of Class A common stock upon exchange of limited partnership interests	34,889	157,547	11,388
Issuance Of Class Common Stock And Limited Partnership Interests For Acquisitions	$ 2,710	$ 1,160	$ 1,578