Equity method investment - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Technology, trade name and customer relationship intangibles	$ 60,963,513		$ 60,963,513		$ 15,104,038
Amortization of Intangible Assets	1,471,568	$ 846,615	2,667,697	$ 1,719,830
Dividends received from equity method investment			14,916,867	21,824,256
Bankers Healthcare Group, LLC
Schedule of Equity Method Investments [Line Items]
Technology, trade name and customer relationship intangibles	15,100,000		15,100,000		$ 16,800,000
Amortization of Intangible Assets	832,000	575,000	1,700,000	953,000
Accretion income	767,000	303,000	1,600,000	1,200,000
Dividends received from equity method investment	12,500,000	16,500,000	14,900,000	21,800,000
Loan face amount	$ 0	$ 0	$ 0	$ 0