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Adoption of Accounting Pronouncements Adoption of Accounting Pronouncements (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Undistributed (gains) losses of equity method investments |  | $ (8,341) | $ (5,362) | $ 318
Distributions in excess of current year income of equity method investments |  | 2,924 | 552 | 0
Increase in other assets |  | (372) | (2,643) | (4,979)
Net cash provided by operating activities |  | 454,944 | 379,545 | 329,509
Distributions from other investments |  | 28,379 | 21,843 | 24,202
Net cash used in investing activities |  | (435,688) | (332,658) | (320,736)
Operating Lease, Right-of-Use Asset |  | 20,800 |  |
Operating Lease, Liability |  | 20,400 |  |
Finance Lease, Right-of-Use Asset |  | 900 |  |
Finance Lease, Liability |  | 900 |  |
Previously Reported [Member] |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Undistributed (gains) losses of equity method investments |  |  | (6,393) | (2,316)
Distributions in excess of current year income of equity method investments |  |  | 0 | 0
Increase in other assets |  |  | (9,872) | (30,071)
Net cash provided by operating activities |  |  | 370,733 | 301,783
Distributions from other investments |  |  | 23,426 | 26,837
Net cash used in investing activities |  |  | (331,075) | (318,101)
Accounting Standards Update 2016-01 [Member] |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Cumulative effect adjustment |  | 30,726 | 0 | 0
Accumulated other comprehensive (loss) income [Member] |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Cumulative effect adjustment | [1] |  | 25,019 |
Accumulated other comprehensive (loss) income [Member] | Accounting Standards Update 2016-01 [Member] |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Cumulative effect adjustment |  | 30,726 | 0 | 0
Accumulated other comprehensive (loss) income [Member] | Accounting Standards Update 2018-02 [Member] |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Cumulative effect adjustment |  | (5,707) | 0 | 0
Retained Earnings [Member] | Accounting Standards Update 2016-01 [Member] |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Cumulative effect adjustment |  | (30,726) | 0 | 0
Retained Earnings [Member] | Accounting Standards Update 2018-02 [Member] |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Cumulative effect adjustment |  | 5,707 | $ 0 | $ 0
Retained Earnings [Member] | Accounting Standards Update 2016-02 [Member] |  |  |  |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |  |  |  |
Cumulative effect adjustment |  | $ (1,000) |  |
[1] | Upon adoption of ASU 2016-01 and ASU 2018-02 in the first quarter of 2018, we recognized a $25.0 million cumulative-effect adjustment to the opening balance of AOCI, which represents the after-tax net unrealized gain on our equity portfolio as of December 31, 2017 and the one-time reclassification from AOCI to retained earnings for the stranded tax assets that were created in AOCI from the enactment of Tax Reform. See Note 3. "Adoption of Accounting Pronouncements" above for additional information.

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