Revenue (Disaggregation of Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Total	$ 115,065	$ 113,971	$ 116,508	$ 126,640	$ 118,080	$ 114,846	$ 117,132	$ 126,037	$ 472,184	$ 476,095	$ 355,561
Benefit Administration Service and COBRA
Disaggregation of Revenue [Line Items]
Total									401,340	407,476
Interchange
Disaggregation of Revenue [Line Items]
Total									50,907	50,229
Other revenue
Disaggregation of Revenue [Line Items]
Total									$ 19,937	$ 18,390