Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital from Treasury Stock Transactions	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss), net of tax	Redeemable Noncontrolling Interest in Subsidiaries/ Temporary Equity
Balance, beginning of period at Dec. 31, 2017	$ 761,215	$ 343,378	$ 0	$ 697,359	$ (278,732)	$ (790)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	60,331			60,331			$ (325)
Other Comprehensive Income (Loss), net of tax	277					277
Stock Award Activity	7,067	6,966		(10,721)	10,822
Dividends Declared	(25,265)			(25,265)
Purchase of Treasury Stock	(3,876)				(3,876)
Balance, end of period at Mar. 31, 2018	799,620	350,344	0	721,829	(271,786)	(767)
Balance, beginning of period, Temporary Equity at Dec. 31, 2017							30,163
Increase (Decrease) in Temporary Equity [Roll Forward]
Net Income	60,331			60,331			(325)
Other Comprehensive Income (Loss), net of tax	277					277
Subscriptions—Redeemable Noncontrolling Interest Holders							500
Distributions to Noncontrolling Interest in Subsidiaries							(1,684)
Balance, end of period, Temporary Equity at Mar. 31, 2018							28,654
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	38,822			38,822			(155)
Other Comprehensive Income (Loss), net of tax	(722)					(722)
Stock Award Activity	5,900	5,794		(567)	673
Dividends Declared	(27,331)			(27,331)
Purchase of Treasury Stock	(17,164)				(17,164)
Balance, end of period at Jun. 30, 2018	799,125	356,138	0	732,753	(288,277)	(1,489)
Increase (Decrease) in Temporary Equity [Roll Forward]
Net Income	38,822			38,822			(155)
Other Comprehensive Income (Loss), net of tax	(722)					(722)
Subscriptions—Redeemable Noncontrolling Interest Holders							663
Consolidation (Deconsolidation)							(1,751)
Distributions to Noncontrolling Interest in Subsidiaries							(6,427)
Balance, end of period, Temporary Equity at Jun. 30, 2018							20,984
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	59,608			59,608			2,386
Other Comprehensive Income (Loss), net of tax	(3,778)					(3,778)	(1,781)
Stock Award Activity	5,471	5,456	15
Dividends Declared	(27,185)			(27,185)
Purchase of Treasury Stock	(5,877)				(5,877)
Balance, end of period at Sep. 30, 2018	827,364	361,594	15	765,176	(294,154)	(5,267)
Increase (Decrease) in Temporary Equity [Roll Forward]
Net Income	59,608			59,608			2,386
Other Comprehensive Income (Loss), net of tax	(3,778)					(3,778)	(1,781)
Subscriptions—Redeemable Noncontrolling Interest Holders							3,262
Distributions to Noncontrolling Interest in Subsidiaries							(1,667)
Business Acquisition							169,560
Balance, end of period, Temporary Equity at Sep. 30, 2018							192,744
Balance, beginning of period at Dec. 31, 2018	857,121	367,252	0	791,823	(287,337)	(14,617)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	54,546			54,546			65
Other Comprehensive Income (Loss), net of tax	7,664					7,664	3,714
Stock Award Activity	7,110	7,110		(11,830)	11,830
Dividends Declared	(27,217)			(27,217)
Purchase of Treasury Stock	(1,485)				(1,485)
Balance, end of period at Mar. 31, 2019	897,739	374,362	0	807,322	(276,992)	(6,953)
Balance, beginning of period, Temporary Equity at Dec. 31, 2018							182,513
Increase (Decrease) in Temporary Equity [Roll Forward]
Net Income	54,546			54,546			65
Other Comprehensive Income (Loss), net of tax	7,664					7,664	3,714
Subscriptions—Redeemable Noncontrolling Interest Holders							42
Stock Award Activity							2,126
Distributions to Noncontrolling Interest in Subsidiaries							(2,260)
Balance, end of period, Temporary Equity at Mar. 31, 2019							186,200
Balance, beginning of period at Dec. 31, 2018	857,121	367,252	0	791,823	(287,337)	(14,617)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Purchase of Treasury Stock					(4,100)
Balance, end of period at Sep. 30, 2019	950,497	386,378	104	871,774	(279,472)	(28,287)
Balance, beginning of period, Temporary Equity at Dec. 31, 2018							182,513
Balance, end of period, Temporary Equity at Sep. 30, 2019							199,492
Balance, beginning of period at Mar. 31, 2019	897,739	374,362	0	807,322	(276,992)	(6,953)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	62,724			62,724			1,116
Other Comprehensive Income (Loss), net of tax	(9,539)					(9,539)	(4,600)
Stock Award Activity	6,240	6,069	103		68
Dividends Declared	(27,323)			(27,323)
Change in Estimated Redemption Value of Redeemable Noncontrolling Interests	(16,604)			(16,604)			16,604
Purchase of Treasury Stock	(709)				(709)
Balance, end of period at Jun. 30, 2019	912,528	380,431	103	826,119	(277,633)	(16,492)
Balance, beginning of period, Temporary Equity at Mar. 31, 2019							186,200
Increase (Decrease) in Temporary Equity [Roll Forward]
Net Income	62,724			62,724			1,116
Other Comprehensive Income (Loss), net of tax	(9,539)					(9,539)	(4,600)
Subscriptions—Redeemable Noncontrolling Interest Holders							1,822
Stock Award Activity							1,773
Distributions to Noncontrolling Interest in Subsidiaries							(541)
Business Acquisition							(386)
Change in Estimated Redemption Value of Redeemable Noncontrolling Interests	(16,604)			(16,604)			16,604
Balance, end of period, Temporary Equity at Jun. 30, 2019							201,988
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	72,962			72,962			623
Other Comprehensive Income (Loss), net of tax	(11,795)					(11,795)	(5,544)
Stock Award Activity	5,969	5,947	1		21
Dividends Declared	(27,307)			(27,307)
Purchase of Treasury Stock	(1,860)				(1,860)
Balance, end of period at Sep. 30, 2019	950,497	$ 386,378	$ 104	871,774	$ (279,472)	(28,287)
Increase (Decrease) in Temporary Equity [Roll Forward]
Net Income	72,962			$ 72,962			623
Other Comprehensive Income (Loss), net of tax	$ (11,795)					$ (11,795)	(5,544)
Subscriptions—Redeemable Noncontrolling Interest Holders							687
Stock Award Activity							2,125
Distributions to Noncontrolling Interest in Subsidiaries							(387)
Balance, end of period, Temporary Equity at Sep. 30, 2019							$ 199,492