Significant Accounting Policies, Fair Value Disclosures (Details) - Recurring [Member] - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Fair Value Hierarchy [Roll Forward]
Cash	$ 20
Money market funds	15,933	$ 9,859
Certificates of deposits	4,084	3,595
Commercial paper	3,998	2,996
Corporate notes and bonds	31,589	45,771
U.S. government agency securities	4,502	2,000
Total	60,126	64,221
Level 1 [Member]
Fair Value Hierarchy [Roll Forward]
Cash	20
Money market funds	15,933	9,859
Certificates of deposits	0	0
Commercial paper	0	0
Corporate notes and bonds	0	0
U.S. government agency securities	0	0
Total	15,953	9,859
Level 2 [Member]
Fair Value Hierarchy [Roll Forward]
Cash	0
Money market funds	0	0
Certificates of deposits	4,084	3,595
Commercial paper	3,998	2,996
Corporate notes and bonds	31,589	45,771
U.S. government agency securities	4,502	2,000
Total	44,173	54,362
Level 3 [Member]
Fair Value Hierarchy [Roll Forward]
Cash	0
Money market funds	0	0
Certificates of deposits	0	0
Commercial paper	0	0
Corporate notes and bonds	0	0
U.S. government agency securities	0	0
Total	$ 0	$ 0