Investments in Foreign Joint Venture - Schedule of Activity in Investment in Foreign Joint Ventures (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Investments in foreign joint ventures:
Balance, beginning of year			$ 10,947
Equity in earnings	$ 251	$ 98	706	$ 284
Dividend paid			(1,127)
Foreign currency translation adjustment			(777)
Balance, end of year	9,749		9,749
Components of investments in foreign joint ventures:
Investment in joint ventures	2,033		2,033
Undistributed earnings	7,545		7,545
Foreign currency translation	171		171
Investments, end of period	9,749		9,749		$ 10,947
BOMAY
Investments in foreign joint ventures:
Balance, beginning of year			10,736
Equity in earnings			706
Dividend paid			(1,127)
Foreign currency translation adjustment			(566)
Balance, end of year	9,749		9,749
Components of investments in foreign joint ventures:
Investment in joint ventures	2,033		2,033
Undistributed earnings	7,545		7,545
Foreign currency translation	171		171
Investments, end of period	$ 9,749		9,749
MIEFE
Investments in foreign joint ventures:
Balance, beginning of year			211
Foreign currency translation adjustment			$ (211)