Schedule III - Real Estate and Accumulated Depreciation and Amortization - Schedule of Changes in Real Estate Assets and Accumulated Depreciation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investment in real estate:
Balance at beginning of year	$ 970,964	$ 782,166	$ 783,233
Acquisitions and capital expenditures	84,069	205,598	19,097
Impairments	(7,950)	(10,623)	(13,590)
Sales and condemnations	(3,091)	(4,520)	(6,379)
Lease expirations/settlements	(886)	(1,657)	(195)
Balance at end of year	1,043,106	970,964	782,166
Accumulated depreciation and amortization:
Balance at beginning of year	133,353	120,576	107,370
Depreciation and amortization	20,549	17,018	16,629
Impairments	(1,780)	(1,301)	(776)
Sales and condemnations	(530)	(1,229)	(2,559)
Lease expirations/settlements	(901)	(1,711)	(88)
Balance at end of year	$ 150,691	$ 133,353	$ 120,576