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Investments - Summary of Investments (Detail) (USD $)
In Thousands, unless otherwise specified
Jun. 30, 2014
Dec. 31, 2013
Investments Schedule [Abstract]    
Marketable securities $ 56,403 $ 28,968
Equity method investments 4,150 4,070
Nonqualified retirement plan assets 4,546 4,220
Total investments $ 65,099 $ 37,258