Debt (Build-to-suit Lease Obligation) (Details) - Discovery Hub [Member] $ in Millions |
3 Months Ended | |
---|---|---|
Mar. 31, 2018
USD ($)
|
Oct. 31, 2017
ft²
|
|
Debt Instrument [Line Items] | ||
Build to suit lease area of land | ft² | 312,000 | |
Build to suit lease project costs paid by third party owner lessor | $ | $ 19 |