Schedule III - Real Estate and Accumulated Depreciation and Amortization - Schedule of Changes in Real Estate Assets and Accumulated Depreciation (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Investment in real estate:
Balance at beginning of year	$ 570,275	$ 562,316	$ 615,854
Acquisitions and capital expenditures	79,259	76,016	10,976
Impairment	(24,620)	(23,238)	(23,354)
Sales and condemnations	(25,786)	(42,884)	(40,381)
Lease expirations/settlements	(3,169)	(1,935)	(779)
Balance at end of year	595,959	570,275	562,316
Accumulated depreciation and amortization:
Balance at beginning of year	103,452	116,768	137,117
Depreciation and amortization expense	9,777	9,231	13,375
Impairment	(3,086)	(9,813)	(9,412)
Sales and condemnations	(6,544)	(11,474)	(23,533)
Lease expirations/settlements	(2,909)	(1,260)	(779)
Balance at end of year	$ 100,690	$ 103,452	$ 116,768