Joint Ventures - Condensed Balance Sheets (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Assets:
Cash	$ 493,761	$ 396,619	$ 318,982	$ 425,316
Liabilities and equity:
Equity	1,408,280	1,304,441
Total liabilities and shareholders' equity	2,742,299	2,643,943
Consolidated Joint Venture
Assets:
Cash	1,210	1,214
Other assets	38	37
Total assets	1,248	1,251
Liabilities and equity:
Accrued expenses	547	550
Equity	701	701
Total liabilities and shareholders' equity	$ 1,248	$ 1,251