Segment Reporting (Schedule of Capital Additions and Acquisitions by Reportable Segments) (Details) - USD ($) $ in Thousands |
3 Months Ended | 12 Months Ended | |||
|---|---|---|---|---|---|
Mar. 31, 2019 |
Mar. 31, 2018 |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| Capital additions and acquisitions by segment [Line Items] | |||||
| Total capital additions and acquisitions | $ 1,073 | $ 57,842 | $ 232,915 | $ 636,883 | $ 543,700 |
| Operating Segments [Member] | Data Centers [Member] | |||||
| Capital additions and acquisitions by segment [Line Items] | |||||
| Total capital additions and acquisitions | 995 | 52,213 | 114,944 | 472,438 | 314,030 |
| Operating Segments [Member] | Healthcare [Member] | |||||
| Capital additions and acquisitions by segment [Line Items] | |||||
| Total capital additions and acquisitions | $ 78 | $ 5,629 | $ 117,971 | $ 164,445 | $ 229,670 |