Financial Instruments Measured at Fair Value - AFS (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Marubun [Member]
Schedule of Available-for-sale Securities [Line Items]
Available For Sale Investment Ownership Percentage	8.40%
Cost basis	$ 10,016	$ 10,016
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax	7,763	3,806
Fair value	17,779	13,822
Mutual Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost basis	17,743	18,097
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax	9,590	5,996
Fair value	$ 27,333	$ 24,093