Schedule III - Real Estate and Accumulated Depreciation and Amortization Part 2 (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Investments In Real Estate [Line Items]
Total Investment in Real Estate	$ 970,964	$ 782,166	$ 783,233	$ 595,959
Accumulated Depreciation And Amortization Description [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	914,488
Cost Capitalized Subsequent to Initial Investment	56,476
Land	589,497
Building and Improvements	381,467
Total Investment in Real Estate	970,964
Accumulated Depreciation and Amortization	133,353
CALIFORNIA [Member] | Accumulated Depreciation And Amortization Description [Member] | Phelan One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	4,611
Land	3,276
Building and Improvements	1,335
Total Investment in Real Estate	4,611
Accumulated Depreciation and Amortization	$ 227
Date of Initial Leasehold or Acquisition Investment	2015
CALIFORNIA [Member] | Accumulated Depreciation And Amortization Description [Member] | Riverside One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 2,130
Land	1,619
Building and Improvements	511
Total Investment in Real Estate	2,130
Accumulated Depreciation and Amortization	$ 106
Date of Initial Leasehold or Acquisition Investment	2015
CALIFORNIA [Member] | Accumulated Depreciation And Amortization Description [Member] | Riverside Two [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 2,737
Land	1,216
Building and Improvements	1,521
Total Investment in Real Estate	2,737
Accumulated Depreciation and Amortization	$ 256
Date of Initial Leasehold or Acquisition Investment	2014
CALIFORNIA [Member] | Accumulated Depreciation And Amortization Description [Member] | Sacramento One [Member]
Schedule Of Investments In Real Estate [Line Items]
Initial Cost of Leasehold or Acquisition Investment to Company	$ 3,193
Land	2,207
Building and Improvements	986
Total Investment in Real Estate	3,193
Accumulated Depreciation and Amortization	$ 167
Date of Initial Leasehold or Acquisition Investment	2015