Significant Accounting Policies (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Depreciation and amortization
Acquired publishing rights	$ 1,303	$ 1,943
Acquired curriculum and technology	2,478	3,510
Pre-publication costs	7,081	6,394
Internally developed software related to product	6,508	6,423
Total amortization included in cost of revenues	17,370	18,270
Trade names and trademarks	419	452
Other intangible assets	849	1,045
Property, equipment and software	2,600	2,712
Total depreciation and amortization included in operating expense	3,868	4,209
Total depreciation and amortization	$ 21,238	$ 22,479