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Basis of Presentation (Narrative) (Details) $ in Thousands | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2018 USD ($) | Jun. 30, 2018 USD ($) segment | Jun. 30, 2017 USD ($) | Dec. 31, 2017 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |
Number of reportable segments | segment |  |  | 4 |  |
Distributed earnings from unconsolidated subsidiaries |  |  | $ 4,595 | $ 12,894 |
Changes in fair value of investments previously reported as cost method investments |  | $ 3,600 | 5,900 |  |
Retained Earnings |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |
Reclassification from AOCI to retained earnings for stranded tax effects |  |  | (3,400) |  |
Accumulated Other Comprehensive Income (Loss) |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |
Reclassification from AOCI to retained earnings for stranded tax effects |  |  | $ 3,400 |  |
Accounting Standards Update 2016-15 |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |
Distributions from unconsolidated subsidiaries, investing activities |  |  |  | (12,900) |
Distributed earnings from unconsolidated subsidiaries |  |  |  | $ 12,900 |
Accounting Standards Update 2016-01 |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |
Cumulative-effect adjustment adoption of ASU | [1] |  |  |  | $ 8,334
Accounting Standards Update 2016-01 | Retained Earnings |  |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |  |
Cumulative-effect adjustment adoption of ASU | [1] |  |  |  | $ 8,334
[1] | See Note 1 for discussion of accounting guidance adopted during the period.

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