Related Party Transactions (Details) |
12 Months Ended | ||
|---|---|---|---|
|
Dec. 31, 2017
USD ($)
ft²
property
item
|
Dec. 31, 2016
USD ($)
|
Dec. 31, 2015
USD ($)
|
|
| Related Party Transaction [Line Items] | |||
| Lease revenue | $ 501,334,000 | $ 506,877,000 | $ 487,041,000 |
| Mack [Member] | |||
| Related Party Transaction [Line Items] | |||
| Due from related parties | 0 | 0 | |
| RG [Member] | |||
| Related Party Transaction [Line Items] | |||
| Related party revenue | $ 1,873,000 | 2,464,000 | 2,542,000 |
| Leased Property [Member] | |||
| Related Party Transaction [Line Items] | |||
| Number of real estate properties | property | 1 | ||
| Lease expiration date | May 2018 | ||
| Number of lease options | item | 2 | ||
| Lease extension period | 3 years | ||
| Leased Property [Member] | Mack [Member] | |||
| Related Party Transaction [Line Items] | |||
| Area Of Real Estate Property | ft² | 7,034 | ||
| Lease revenue | $ 187,000 | $ 193,000 | $ 204,000 |