Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Prepaid expenses and other current assets
Prepaid service contracts – current portion	$ 12,539	$ 6,754
Deferred costs	3,849	6,911
Prepaid postage	3,047	1,492
Rebates	3,004	3,164
Prepaid marketing	1,197	446
Other prepaid expenses and current assets	9,511	6,216
Total prepaid expenses and other current assets	$ 33,147	$ 24,983