Joint Ventures - Condensed Balance Sheets (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Liabilities and equity:
Equity	$ 1,466,808	$ 1,605,492
Total liabilities and shareholders' equity	2,846,065	2,989,279
Consolidated Joint Venture [Member]
Assets:
Cash	1,148	1,069
Other assets	37	37
Assets related to consolidated variable interest entity	1,185	1,106
Liabilities and equity:
Accrued expenses	490	487
Equity	695	619
Total liabilities and shareholders' equity	$ 1,185	$ 1,106