Goodwill and Other Intangible Assets (Schedule of Goodwill and Other Intangible Assets Included in Equity Method Investments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other intangible assets
Gross amount	$ 159,503	$ 148,395
Accumulated impairment losses and amortization	(102,537)	(93,924)
Intangible Assets, Net, Excluding Goodwill [Roll Forward]
Other intangible assets, net, beginning balance	54,471
Other intangible assets, net, ending balance	56,966	54,471
Intangible Assets, Net, Including Goodwill [Roll Forward]
Goodwill and Other intangible assets, net, beginning balance	243,145
Goodwill and Other intangible assets, net, ending balance	237,418	243,145
Investments in other ventures, under equity method
Goodwill
Gross amount	15,098	12,318	$ 12,318
Accumulated impairment losses and amortization	(4,500)	(4,500)	(4,500)
Goodwill	10,598	7,818	7,818
Acquired during the year	2,780
Other intangible assets
Gross amount	62,904	51,796	51,796
Accumulated impairment losses and amortization	(45,766)	(42,880)	(39,934)
Intangible Assets, Net, Excluding Goodwill [Roll Forward]
Other intangible assets, net, beginning balance	8,916	11,862
Acquired during the year	11,108
Amortization	(2,886)	(2,946)
Other intangible assets, net, ending balance	17,138	8,916
Goodwill and Other intangible assets, Total
Gross amount	78,002	64,114	64,114
Accumulated impairment losses and amortization	(50,266)	(47,380)	$ (44,434)
Intangible Assets, Net, Including Goodwill [Roll Forward]
Goodwill and Other intangible assets, net, beginning balance	16,734	19,680
Acquired during the year	13,888
Amortization	(2,886)	(2,946)
Goodwill and Other intangible assets, net, ending balance	$ 27,736	$ 16,734