Goodwill and Other Intangible Assets (Schedule of Intangible Assets and Goodwill) (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
Excluding Equity Method Investments
Goodwill
Gross amount	199,889	199,889	$ 199,889
Accumulated impairment losses and amortization	(2,299)	(2,299)	(2,299)
Goodwill	197,590	197,590	197,590
Other intangible assets
Gross amount	96,599	96,599	96,599
Accumulated impairment losses and amortization	(56,771)	(51,044)	(43,003)
Intangible Assets, Net, Excluding Goodwill [Roll Forward]
Other intangible assets, net, beginning balance	45,555	53,596
Amortization	(5,727)	(8,041)
Other intangible assets, net, ending balance	39,828	45,555
Goodwill and Other intangible assets, Total
Gross amount	296,488	296,488	296,488
Accumulated impairment losses and amortization	(59,070)	(53,343)	$ (45,302)
Intangible Assets, Net, Including Goodwill [Roll Forward]
Goodwill and Other intangible assets, net, beginning balance	243,145	251,186
Amortization	(5,727)	(8,041)
Goodwill and Other intangible assets, net, ending balance	$ 237,418	$ 243,145