Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Class A	Common Stock	Common Stock Class A	Common Stock Class B	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Loss, Net of Tax	Total Shareholders' Equity	Nonredeemable Noncontrolling Interest in Subsidiary	Redeemable Noncontrolling Interest in Subsidiaries/ Temporary Equity
Common stock, beginning balance (in shares) at Dec. 31, 2015				9,000	104,094,027
Treasury stock, beginning balance (in shares) at Dec. 31, 2015						5,411,429
Beginning balance at Dec. 31, 2015	$ 648,972		$ 298,579			$ (191,939)	$ 545,785	$ (4,609)	$ 647,816	$ 1,156
Temporary equity, beginning balance at Dec. 31, 2015											$ 8,734
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	218,312						208,919		208,919	9,393	3,202
Other Comprehensive Income (Loss), net of tax	3,255							3,255	3,255		(13)
Subscriptions – Redeemable Noncontrolling Interest Holders											17,868
Consolidation/(Deconsolidation)											(4,579)
Stock Award Activity (in shares)					948,860
Stock Award Activity (in shares)						(948,860)
Stock Award Activity	23,715		22,280			$ 20,150	(18,715)		23,715
Dividends Declared	(205,329)						(205,329)		(205,329)
Distributions to Noncontrolling Interest in Subsidiaries	(9,591)									(9,591)	(8,700)
Purchase of Treasury Stock (in shares)					(3,053,204)
Purchase of Treasury Stock (in shares)						3,053,204
Purchase of Treasury Stock	(83,593)					$ (83,593)			(83,593)
Common stock, ending balance (in shares) at Dec. 31, 2016				9,000	101,989,683
Treasury stock, ending balance (in shares) at Dec. 31, 2016						7,515,773
Ending balance at Dec. 31, 2016	595,784		320,982			$ (255,382)	529,749	(523)	594,826	958
Temporary equity, ending balance at Dec. 31, 2016											31,362
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	291,817						291,341		291,341	476	3,084
Other Comprehensive Income (Loss), net of tax	(267)							(267)	(267)
Subscriptions – Redeemable Noncontrolling Interest Holders											4,687
Consolidation/(Deconsolidation)											(67)
Stock Award Activity (in shares)					952,570
Stock Award Activity (in shares)						(952,570)
Stock Award Activity	23,695		22,396			$ 23,607	(22,308)		23,695
Dividends Declared	(101,423)						(101,423)		(101,423)
Distributions to Noncontrolling Interest in Subsidiaries	(1,434)									(1,434)	(8,903)
Purchase of Treasury Stock (in shares)					(1,841,800)
Purchase of Treasury Stock (in shares)						1,841,800
Purchase of Treasury Stock	$ (46,957)					$ (46,957)			(46,957)
Common stock, ending balance (in shares) at Dec. 31, 2017		9,000		9,000	101,100,453
Treasury stock, ending balance (in shares) at Dec. 31, 2017	8,405,003					8,405,003
Ending balance at Dec. 31, 2017	$ 761,215		343,378			$ (278,732)	697,359	(790)	761,215	0
Temporary equity, ending balance at Dec. 31, 2017											30,163
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	220,297						220,297		220,297		2,002
Other Comprehensive Income (Loss), net of tax	(13,573)							(13,573)	(13,573)		(6,009)
Subscriptions – Redeemable Noncontrolling Interest Holders											7,040
Consolidation/(Deconsolidation)											(1,751)
Stock Award Activity (in shares)					908,719
Stock Award Activity (in shares)						(908,719)
Stock Award Activity	25,318		23,874			$ 20,495	(19,051)		25,318
Dividends Declared	(106,907)						(106,907)		(106,907)
Distributions to Noncontrolling Interest in Subsidiaries											(18,492)
Business Acquisition											(169,560)
Purchase of Treasury Stock (in shares)					(1,205,790)
Purchase of Treasury Stock (in shares)						1,205,790
Purchase of Treasury Stock	$ (29,100)					$ (29,100)			(29,100)
Common stock, ending balance (in shares) at Dec. 31, 2018		9,000		9,000	100,803,382
Treasury stock, ending balance (in shares) at Dec. 31, 2018	8,702,074					8,702,074
Ending balance at Dec. 31, 2018	$ 857,121		$ 367,252			$ (287,337)	$ 791,823	$ (14,617)	$ 857,121	$ 0
Temporary equity, ending balance at Dec. 31, 2018											$ 182,513