Investment in Real Estate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Real Estate And Accumulated Depreciation Disclosure [Abstract]
Balance, beginning of period	$ 1,145,630	$ 1,151,339
Additions during period:
Acquisitions	49,734	147,633
Improvements to land and building	22,701	18,332
Deductions during period:
Dispositions, impairments and deconsolidation of real estate	(363,419)	(171,674)
Balance, end of period:	$ 854,646	$ 1,145,630