Other Non-Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Other Non-Current Liabilities
Uncertain tax positions	$ 10,379	$ 7,762
Accrued deferred compensation	4,006	2,885
Accrued purchase liability		1,250
Other	142	1,539
Other non-current liabilities	$ 14,527	$ 13,436