Credit Facility (Tables)
3 Months Ended 12 Months Ended
Mar. 31, 2019
Dec. 31, 2018
Debt Instrument [Line Items]    
Schedule of Secured Credit Facility  
The Company's outstanding secured credit facility as of December 31, 2018 and 2017 consisted of the following (amounts in thousands):
 
 
December 31, 2018
 
December 31, 2017
 
 
 
 
 
Variable rate revolving line of credit
 
$
105,000

 
$
120,000

Variable rate term loan fixed through interest rate swaps
 
100,000

 
100,000

Variable rate term loan
 
150,000

 
—

Total secured credit facility, principal amount outstanding
 
355,000

 
220,000

Unamortized deferred financing costs related to the term loan secured credit facility
 
(2,489
)
 
(601
)
Total secured credit facility, net of deferred financing costs
 
$
352,511

 
$
219,399

Schedule of Future Principal Payments Due on Debt
The principal payments due on the notes payable and secured credit facility for the nine months ending December 31, 2019, and for each of the next four years ending December 31 and thereafter, are as follows (amounts in thousands):
Year
 
Amount
Nine months ending December 31, 2019
 
$
1,681

2020
 
4,530

2021
 
155,207

2022
 
279,922

2023
 
252,712

Thereafter
 
138,429

 
 
$
832,481

 
Secured Credit Facility [Member]    
Debt Instrument [Line Items]    
Schedule of Future Principal Payments Due on Debt  
The principal payments due on the secured credit facility as of December 31, 2018, for each of the next five years ending December 31, are as follows (amounts in thousands):
Year
 
Amount
2019
 
$
—

2020
 
—

2021
 
—

2022
 
105,000

2023
 
250,000

 
 
$
355,000