Joint Ventures - Condensed Balance Sheets (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Liabilities and equity:
Equity	$ 1,607,571	$ 1,605,492
Total liabilities and shareholders' equity	3,009,395	2,989,279
Consolidated Joint Venture [Member]
Assets:
Cash	1,128	1,069
Other assets	37	37
Assets related to consolidated variable interest entity	1,165	1,106
Liabilities and equity:
Accrued expenses	484	487
Equity	681	619
Total liabilities and shareholders' equity	$ 1,165	$ 1,106