Investments - Summary of Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Investments Schedule [Abstract]
Marketable securities	$ 41,496	$ 50,251
Equity method investments	9,007	7,209
Nonqualified retirement plan assets	5,310	5,063
Other investments	925	925
Total investments	$ 56,738	$ 63,448