Condensed Consolidating Statement Of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Condensed Consolidating Financial Statements [Line Items]
Net cash provided by operating activities	$ 4,552	$ 24,214
CASH FLOWS FROM INVESTING ACTIVITIES:
Investment in property and equipment	(4,996)	(4,718)
Investment in intangible assets	(1,193)	(2,088)
Business acquisition, net of cash acquired	(231,317)	0
Contributions to equity method investments	(1,455)	(31,610)
Distributions from equity method investments	766	510
Issuance of mezzanine and other notes receivable	(2,500)	(9,863)
Collections of mezzanine and other notes receivable	150	522
Purchases of investments, employee benefit plans	1,669	1,424
Proceeds from sales of investments, employee benefit plans	1,029	843
Advances to and investments in affiliates	0	0
Divestment in affiliates	0	0
Other items, net	0	(4)
Net cash used in investing activities	(241,185)	(47,832)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net borrowings pursuant to revolving credit facilities	70,000	22,800
Principal payments on long-term debt	(111)	(153)
Proceeds from issuance of long term debt	212	0
Purchase of treasury stock	(41,869)	(7,271)
Debt issuance costs	(914)	0
Proceeds from exercise of stock options	23,052	4,963
Proceeds from contributions from affiliates	0	0
Distributions to affiliates	0	0
Dividends paid	(12,265)	(12,139)
Net cash provided by financing activities	38,105	8,200
Net change in cash and cash equivalents	(198,528)	(15,418)
Effect of foreign exchange rate changes on cash and cash equivalents	26	427
Cash and cash equivalents at beginning of period	235,336	202,463
Cash and cash equivalents at end of period	36,834	187,472
Parent
Condensed Consolidating Financial Statements [Line Items]
Net cash provided by operating activities	197,590	(13,926)
CASH FLOWS FROM INVESTING ACTIVITIES:
Investment in property and equipment	(2,904)	(3,832)
Investment in intangible assets	(1,193)	(1,369)
Business acquisition, net of cash acquired	(231,317)
Contributions to equity method investments	0	0
Distributions from equity method investments	0	0
Issuance of mezzanine and other notes receivable	(2,500)	(330)
Collections of mezzanine and other notes receivable	150	522
Purchases of investments, employee benefit plans	0	0
Proceeds from sales of investments, employee benefit plans	0	0
Advances to and investments in affiliates	0	0
Divestment in affiliates	0	0
Other items, net		0
Net cash used in investing activities	(237,764)	(5,009)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net borrowings pursuant to revolving credit facilities	70,000	22,800
Principal payments on long-term debt	0	0
Proceeds from issuance of long term debt	0
Purchase of treasury stock	(41,869)	(7,271)
Debt issuance costs	0
Proceeds from exercise of stock options	23,052	4,963
Proceeds from contributions from affiliates	0	0
Distributions to affiliates	0	0
Dividends paid	(12,265)	(12,139)
Net cash provided by financing activities	38,918	8,353
Net change in cash and cash equivalents	(1,256)	(10,582)
Effect of foreign exchange rate changes on cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	12,671	14,696
Cash and cash equivalents at end of period	11,415	4,114
Guarantor Subsidiaries
Condensed Consolidating Financial Statements [Line Items]
Net cash provided by operating activities	4,159	33,440
CASH FLOWS FROM INVESTING ACTIVITIES:
Investment in property and equipment	(837)	(710)
Investment in intangible assets	0	(719)
Business acquisition, net of cash acquired	0
Contributions to equity method investments	(1,432)	(31,592)
Distributions from equity method investments	564	0
Issuance of mezzanine and other notes receivable	0	0
Collections of mezzanine and other notes receivable	0	0
Purchases of investments, employee benefit plans	1,669	1,424
Proceeds from sales of investments, employee benefit plans	1,029	843
Advances to and investments in affiliates	(2,450)	(484)
Divestment in affiliates	650	510
Other items, net		0
Net cash used in investing activities	(4,145)	(33,576)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net borrowings pursuant to revolving credit facilities	0	0
Principal payments on long-term debt	0	0
Proceeds from issuance of long term debt	0
Purchase of treasury stock	0	0
Debt issuance costs	0
Proceeds from exercise of stock options	0	0
Proceeds from contributions from affiliates	0	0
Distributions to affiliates	0	0
Dividends paid	0	0
Net cash provided by financing activities	0	0
Net change in cash and cash equivalents	14	(136)
Effect of foreign exchange rate changes on cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	38	159
Cash and cash equivalents at end of period	52	23
Non-Guarantor Subsidiaries
Condensed Consolidating Financial Statements [Line Items]
Net cash provided by operating activities	5,087	4,700
CASH FLOWS FROM INVESTING ACTIVITIES:
Investment in property and equipment	(1,255)	(176)
Investment in intangible assets	0	0
Business acquisition, net of cash acquired	0
Contributions to equity method investments	(23)	(18)
Distributions from equity method investments	202	510
Issuance of mezzanine and other notes receivable	0	(9,533)
Collections of mezzanine and other notes receivable	0	0
Purchases of investments, employee benefit plans	0	0
Proceeds from sales of investments, employee benefit plans	0	0
Advances to and investments in affiliates	0	0
Divestment in affiliates	0	0
Other items, net		(4)
Net cash used in investing activities	(1,076)	(9,221)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net borrowings pursuant to revolving credit facilities	0	0
Principal payments on long-term debt	(111)	(153)
Proceeds from issuance of long term debt	212
Purchase of treasury stock	0	0
Debt issuance costs	(914)
Proceeds from exercise of stock options	0	0
Proceeds from contributions from affiliates	2,450	484
Distributions to affiliates	(650)	(510)
Dividends paid	(202,284)	0
Net cash provided by financing activities	(201,297)	(179)
Net change in cash and cash equivalents	(197,286)	(4,700)
Effect of foreign exchange rate changes on cash and cash equivalents	26	427
Cash and cash equivalents at beginning of period	222,627	187,608
Cash and cash equivalents at end of period	25,367	183,335
Eliminations
Condensed Consolidating Financial Statements [Line Items]
Net cash provided by operating activities	(202,284)	0
CASH FLOWS FROM INVESTING ACTIVITIES:
Investment in property and equipment	0	0
Investment in intangible assets	0	0
Business acquisition, net of cash acquired	0
Contributions to equity method investments	0	0
Distributions from equity method investments	0	0
Issuance of mezzanine and other notes receivable	0	0
Collections of mezzanine and other notes receivable	0	0
Purchases of investments, employee benefit plans	0	0
Proceeds from sales of investments, employee benefit plans	0	0
Advances to and investments in affiliates	2,450	484
Divestment in affiliates	(650)	(510)
Other items, net		0
Net cash used in investing activities	1,800	(26)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net borrowings pursuant to revolving credit facilities	0	0
Principal payments on long-term debt	0	0
Proceeds from issuance of long term debt	0
Purchase of treasury stock	0	0
Debt issuance costs	0
Proceeds from exercise of stock options	0	0
Proceeds from contributions from affiliates	(2,450)	(484)
Distributions to affiliates	650	510
Dividends paid	202,284	0
Net cash provided by financing activities	200,484	26
Net change in cash and cash equivalents	0	0
Effect of foreign exchange rate changes on cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and cash equivalents at end of period	$ 0	$ 0