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Summary of Significant Accounting Policies (Income Taxes) (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2018 | Sep. 30, 2018 | Jun. 30, 2018 | Mar. 31, 2018 | Dec. 31, 2017 | Sep. 30, 2017 | Jun. 30, 2017 | Mar. 31, 2017 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Tax Treatment Of Dividend |  |  |  |  |  |  |  |  |  |  |
Internal taxable income distribution policy (in percentage) |  |  |  |  |  |  |  |  | 100.00% |  |
Differences between book and tax basis | $ 186,559 |  |  |  |  |  |  |  | $ 186,559 |  |
Reconciliation of Net Income to Estimated Taxable Income |  |  |  |  |  |  |  |  |  |  |
Net income | $ 9,971 | $ 15,003 | $ 17,570 | $ (9,700) | $ 17,883 | $ 20,299 | $ 20,660 | $ 21,667 | 32,844 | $ 80,509 | $ 86,477
Straight-line rent adjustments |  |  |  |  |  |  |  |  | 5,870 | 4,250 | 2,347
Depreciation and amortization timing differences |  |  |  |  |  |  |  |  | (6,586) | 3,084 | (14,534)
Change in fair value of marketable securities (see Note 5) |  |  |  |  |  |  |  |  | 11,990 | 0 | 0
Loss from discontinued operations (see Note 6) |  |  |  |  |  |  |  |  | 23,797 | 0 | 0
Other |  |  |  |  |  |  |  |  | 440 | (343) | 2,975
Estimated taxable income |  |  |  |  |  |  |  |  | $ 68,355 | $ 87,500 | $ 77,265
Minimum |  |  |  |  |  |  |  |  |  |  |
Tax Treatment Of Dividend |  |  |  |  |  |  |  |  |  |  |
Real estate investment trust distributable income policy (in percentage) |  |  |  |  |  |  |  |  | 90.00% |  |
Ordinary Income |  |  |  |  |  |  |  |  |  |  |
Tax Treatment Of Dividend |  |  |  |  |  |  |  |  |  |  |
Payments of dividends net percent |  |  |  |  |  |  |  |  | 100.00% | 99.50% | 97.70%
Long Term Capital Gain |  |  |  |  |  |  |  |  |  |  |
Tax Treatment Of Dividend |  |  |  |  |  |  |  |  |  |  |
Payments of dividends net percent |  |  |  |  |  |  |  |  |  | 0.50% | 2.30%

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