Income Taxes - Rate reconciliation (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of income tax (expense) benefit:
Federal statutory rate	34.00%	34.00%	34.00%
State income taxes, net of federal income tax	(1.60%)	(1.40%)	3.50%
Change in fair value of warrant liabilities	3.80%	(37.40%)	(6.00%)
Change in valuation allowance	(42.10%)	(1.10%)	7.10%
Non-deductible stock compensation	(2.70%)	(6.00%)	(5.10%)
Change in fair value of contingent consideration			(4.10%)
Non-deductible expenses and other	(0.90%)	(1.00%)	(2.40%)
Effective income tax rate	(9.50%)	(12.90%)	27.00%