Schedule of Financial Instruments Having Difference Between Carrying Amount and Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Investment in direct financing lease, Carrying Amount	$ 684	$ 3,223
Note receivable from APM, Carrying Amount	2,920	3,504
Debt, Carrying Amount	(1,455,000)	(1,464,000)
Investment in direct financing lease, Fair Value	694	3,408
Note receivable from APM, Fair Value	4,647	5,864
Debt, Fair Value	$ (1,459,625)	$ (1,452,719)