Consolidated Statements Of Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member] Common Class A [Member]	Common Stock [Member] Common Class B [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income [Member]	Accumulated Deficit [Member]	Common Class A [Member]	Common Class B [Member]	Total
Balance, Shares at Dec. 31, 2018	43,721,000	34,303,000
Balance at Dec. 31, 2018	$ 437	$ 343	$ 415,281	$ 1,502	$ (101,326)			$ 316,237
Net income					2,018			2,018
Other comprehensive income				1,057				$ 1,057
Repurchase and retirement of common stock, Shares	(12,000)							(12,402)
Repurchase and retirement of common stock			(122)		(799)			$ (921)
Stock issuances, net, Shares	25,000
Stock issuances, net			1,377					1,377
Conversion of Class B common stock by shareholder, Shares	3,204,000	(3,204,000)
Conversion of Class B common stock by shareholder	$ 32	$ (32)
Taxes paid related to net settlement upon vesting of equity awards			(242)					(242)
Cash dividends declared			10		(18,742)			(18,732)
Stock-based compensation			24,492					24,492
Balance, Shares at Jun. 30, 2019	46,938,000	31,099,000
Balance at Jun. 30, 2019	$ 469	$ 311	440,796	2,559	(118,849)			325,286
Balance, Shares at Mar. 31, 2019	43,739,000	34,303,000
Balance at Mar. 31, 2019	$ 437	$ 343	429,217	2,262	(119,090)			313,169
Net income					10,414			10,414
Other comprehensive income				297				$ 297
Repurchase and retirement of common stock, Shares	(12,000)							(12,402)
Repurchase and retirement of common stock			(122)		(799)			$ (921)
Stock issuances, net, Shares	7,000
Stock issuances, net			220					220
Conversion of Class B common stock by shareholder, Shares	3,204,000	(3,204,000)
Conversion of Class B common stock by shareholder	$ 32	$ (32)
Taxes paid related to net settlement upon vesting of equity awards			(191)					(191)
Cash dividends declared			8		(9,374)			(9,366)
Stock-based compensation			11,664					11,664
Balance, Shares at Jun. 30, 2019	46,938,000	31,099,000
Balance at Jun. 30, 2019	$ 469	$ 311	440,796	2,559	(118,849)			325,286
Balance, Shares at Dec. 31, 2019	46,181,000	31,099,000				46,181,320	31,099,011
Balance at Dec. 31, 2019	$ 462	$ 311	405,353	2,864	(133,664)			275,326
Net income					69,962			69,962
Other comprehensive income				(100)				$ (100)
Repurchase and retirement of common stock, Shares								0
Stock issuances, net, Shares	137,000
Stock issuances, net	$ 1		1,411					$ 1,412
Taxes paid related to net settlement upon vesting of equity awards			(2,620)					(2,620)
Cash dividends declared			4		(18,583)			(18,579)
Stock-based compensation			20,054					20,054
Balance, Shares at Jun. 30, 2020	46,318,000	31,099,000				46,318,317	31,099,011
Balance at Jun. 30, 2020	$ 463	$ 311	424,202	2,764	(82,285)			345,455
Balance, Shares at Mar. 31, 2020	46,311,000	31,099,000
Balance at Mar. 31, 2020	$ 463	$ 311	417,257	836	(116,780)			302,087
Net income					43,789			43,789
Other comprehensive income				1,928				$ 1,928
Repurchase and retirement of common stock, Shares								0
Stock issuances, net, Shares	7,000
Taxes paid related to net settlement upon vesting of equity awards			(48)					$ (48)
Cash dividends declared			4		(9,294)			(9,290)
Stock-based compensation			6,989					6,989
Balance, Shares at Jun. 30, 2020	46,318,000	31,099,000				46,318,317	31,099,011
Balance at Jun. 30, 2020	$ 463	$ 311	$ 424,202	$ 2,764	$ (82,285)			$ 345,455