Income Taxes - Reconciliation of Provision for Income Taxes (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
U.S statutory income taxes rate	35.00%	35.00%	35.00%
Non-deductible expenses	(6.80%)	(2.50%)	(2.40%)
Foreign taxes rate differential	15.10%	(14.20%)	(19.20%)
Change in valuation allowance	(11.90%)	(30.00%)	(18.20%)
State income taxes	18.70%	2.30%	1.80%
Share based compensation	(4.50%)	1.20%
Change in unrecognized taxes expense	(0.80%)	(0.70%)	(1.20%)
Other	(71.90%)	0.40%	0.10%
Effective taxes rate	(27.10%)	(8.50%)	(4.10%)