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, 2019
Other intangible assets
Gross amount	$ 159,503		$ 177,507
Accumulated impairment losses and amortization	(102,537)		(111,639)
Intangible Assets, Net, Excluding Goodwill [Roll Forward]
Other intangible assets, net, ending balance	56,966
Intangible Assets, Net, Including Goodwill [Roll Forward]
Goodwill and Other intangible assets, net, ending balance	237,418
Investments in other ventures, under equity method
Goodwill
Gross amount	15,098	$ 12,318	15,098
Accumulated impairment losses and amortization	(4,500)	(4,500)	(4,500)
Goodwill	10,598	7,818	10,598
Acquired during the year	0	2,780
Other intangible assets
Gross amount	62,904	51,796	62,908
Accumulated impairment losses and amortization	(45,766)	(42,880)	(48,582)
Intangible Assets, Net, Excluding Goodwill [Roll Forward]
Other intangible assets, net, beginning balance	8,916
Acquired during the year	4	11,108
Amortization	(2,816)	(2,886)
Other intangible assets, net, ending balance	17,138	8,916
Goodwill and Other intangible assets, Total
Gross amount	78,002	64,114	78,006
Accumulated impairment losses and amortization	(50,266)	(47,380)	$ (53,082)
Intangible Assets, Net, Including Goodwill [Roll Forward]
Goodwill and Other intangible assets, net, beginning balance	16,734
Acquired during the year	4	13,888
Amortization	(2,816)	(2,886)
Goodwill and Other intangible assets, net, ending balance	$ 27,736	$ 16,734