Joint Ventures - Condensed Balance Sheets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets:
Cash	$ 732,248	$ 689,557	$ 416,037	$ 450,794
Liabilities and equity:
Equity	1,808,562	1,605,492	1,304,441	$ 1,239,165
Total liabilities and shareholders' equity	3,165,933	2,989,279
Consolidated Joint Venture
Assets:
Cash	320	1,069	$ 1,214
Other assets	0	37
Total assets	320	1,106
Liabilities and equity:
Accrued expenses	282	487
Equity	38	619
Total liabilities and shareholders' equity	$ 320	$ 1,106