Marketable Securities, Available-for-sale (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Gain from marketable securities, net	$ 173	$ 429	$ 318	$ 833
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	17,742		17,742		$ 17,627
GROSS UNREALIZED GAINS	49		49		218
Marketable securities, available-for-sale	17,791		17,791		17,845
Total debt securities
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	10,216		10,216		10,116
GROSS UNREALIZED GAINS	49		49		218
Marketable securities, available-for-sale	10,265		10,265		10,334
U.S. Treasury securities
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	450		450		350
GROSS UNREALIZED GAINS	0		0		0
Marketable securities, available-for-sale	450		450		350
Municipal debt securities
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	9,766		9,766		9,766
GROSS UNREALIZED GAINS	49		49		218
Marketable securities, available-for-sale	9,815		9,815		9,984
Time deposits
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	7,526		7,526		7,511
GROSS UNREALIZED GAINS	0		0		0
Marketable securities, available-for-sale	$ 7,526		$ 7,526		$ 7,511