Investments In Securities Investments in Securities (Schedule of Carrying Value and Fair Value of Financial Assets Disclosed) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 36,677	$ 18,694
Accrued interest and dividends	922	946
Equity Securities, Estimated Fair Value	55,065	48,489
Commercial paper and money market funds	18,979	32,787
Equity investments in unconsolidated affiliates, equity method	5,601	5,847
Equity investments in unconsolidated affiliates, measurement alternative	6,818	6,589	$ 5,439
Assets, Fair Value Disclosure	124,062	113,352
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	36,677	18,694
Accrued interest and dividends	922	946
Equity Securities, Estimated Fair Value	55,065	48,489
Commercial paper and money market funds	18,979	32,787
Equity investments in unconsolidated affiliates, equity method	0	0
Equity investments in unconsolidated affiliates, measurement alternative	0	0
Assets, Fair Value Disclosure	111,643	100,916
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Accrued interest and dividends	0	0
Equity Securities, Estimated Fair Value	0	0
Commercial paper and money market funds	0	0
Equity investments in unconsolidated affiliates, equity method	0	0
Equity investments in unconsolidated affiliates, measurement alternative	0	0
Assets, Fair Value Disclosure	0	0
Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Accrued interest and dividends	0	0
Equity Securities, Estimated Fair Value	0	0
Commercial paper and money market funds	0	0
Equity investments in unconsolidated affiliates, equity method	5,601	5,847
Equity investments in unconsolidated affiliates, measurement alternative	6,818	6,589
Assets, Fair Value Disclosure	$ 12,419	$ 12,436