Supplemental Guarantor Condensed Consolidated Financial Statements - Condensed Consolidating Statement of Cash Flows (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operations:
Cash provided by (used in) operating activities	$ 118,279	$ (34,386)
Cash flows from investing activities
Purchase of furniture, equipment and leasehold improvements	(6,654)	(3,506)
Purchase of tangible assets	(400)	0
Proceeds from settlement of company-owned life insurance	284	1,194
Cash used in investing activities	(6,770)	(2,312)
Cash flows from financing activities
Cash dividends paid on Class A non-voting and Class B voting common stock	(4,373)	(4,394)
Cash dividends paid to non-controlling interest	0	(2,448)
Issuance of Class A non-voting common stock	70	0
Payments for Repurchase of Common Stock	0	(7,464)
Payments for employee taxes withheld related to vested share-based awards	(2,529)	(2,232)
Proceeds from Issuance of Long-term Debt		(200,000)
Repayments of Long-term Debt		(150,000)
Debt issuance costs	0	(1,183)
Redemption of senior secured notes	(115,300)	(15,700)
Cash (used in) provided by financing activities	(122,132)	16,579
Net decrease in cash and cash equivalents	(10,623)	(20,119)
Cash and cash equivalents, beginning of period	48,154	64,913
Cash and cash equivalents, end of period	37,531	44,794
Eliminations
Cash flows from operations:
Cash provided by (used in) operating activities	0	0
Cash flows from investing activities
Purchase of furniture, equipment and leasehold improvements	0	0
Purchase of tangible assets	0
Proceeds from settlement of company-owned life insurance	0	0
Cash used in investing activities	0	0
Cash flows from financing activities
Cash dividends paid on Class A non-voting and Class B voting common stock	0	0
Cash dividends paid to non-controlling interest		0
Issuance of Class A non-voting common stock	0
Payments for Repurchase of Common Stock		0
Payments for employee taxes withheld related to vested share-based awards	0	0
Proceeds from Issuance of Long-term Debt		0
Repayments of Long-term Debt		0
Debt issuance costs		0
Redemption of senior secured notes	0	0
Cash (used in) provided by financing activities	0	0
Net decrease in cash and cash equivalents	0	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	0	0
Guarantor Subsidiaries
Cash flows from operations:
Cash provided by (used in) operating activities	1,337	1,679
Cash flows from investing activities
Purchase of furniture, equipment and leasehold improvements	0	0
Purchase of tangible assets	(400)
Proceeds from settlement of company-owned life insurance	0	0
Cash used in investing activities	(400)	0
Cash flows from financing activities
Cash dividends paid on Class A non-voting and Class B voting common stock	0	0
Cash dividends paid to non-controlling interest		0
Issuance of Class A non-voting common stock	0
Payments for Repurchase of Common Stock		0
Payments for employee taxes withheld related to vested share-based awards	0	0
Proceeds from Issuance of Long-term Debt		0
Repayments of Long-term Debt		0
Debt issuance costs		0
Redemption of senior secured notes	0	0
Cash (used in) provided by financing activities	0	0
Net decrease in cash and cash equivalents	937	1,679
Cash and cash equivalents, beginning of period	3,716	10,284
Cash and cash equivalents, end of period	4,653	11,963
Non-Guarantor Subsidiaries
Cash flows from operations:
Cash provided by (used in) operating activities	117,073	(1,616)
Cash flows from investing activities
Purchase of furniture, equipment and leasehold improvements	(6,654)	(3,506)
Purchase of tangible assets	0
Proceeds from settlement of company-owned life insurance	284	1,194
Cash used in investing activities	(6,370)	(2,312)
Cash flows from financing activities
Cash dividends paid on Class A non-voting and Class B voting common stock	0	0
Cash dividends paid to non-controlling interest		(2,448)
Issuance of Class A non-voting common stock	0
Payments for Repurchase of Common Stock		0
Payments for employee taxes withheld related to vested share-based awards	0	0
Proceeds from Issuance of Long-term Debt		0
Repayments of Long-term Debt		0
Debt issuance costs		0
Redemption of senior secured notes	(115,300)	(15,700)
Cash (used in) provided by financing activities	(115,300)	(18,148)
Net decrease in cash and cash equivalents	(4,597)	(22,076)
Cash and cash equivalents, beginning of period	36,996	54,400
Cash and cash equivalents, end of period	32,399	32,324
Parent
Cash flows from operations:
Cash provided by (used in) operating activities	(131)	(34,449)
Cash flows from investing activities
Purchase of furniture, equipment and leasehold improvements	0	0
Purchase of tangible assets	0
Proceeds from settlement of company-owned life insurance	0	0
Cash used in investing activities	0	0
Cash flows from financing activities
Cash dividends paid on Class A non-voting and Class B voting common stock	(4,373)	(4,394)
Cash dividends paid to non-controlling interest		0
Issuance of Class A non-voting common stock	70
Payments for Repurchase of Common Stock		(7,464)
Payments for employee taxes withheld related to vested share-based awards	(2,529)	(2,232)
Proceeds from Issuance of Long-term Debt		200,000
Repayments of Long-term Debt		(150,000)
Debt issuance costs		(1,183)
Redemption of senior secured notes	0	0
Cash (used in) provided by financing activities	(6,832)	34,727
Net decrease in cash and cash equivalents	(6,963)	278
Cash and cash equivalents, beginning of period	7,442	229
Cash and cash equivalents, end of period	$ 479	$ 507