Selected Quarterly Financial Data - Statements of Income (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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	Jun. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Financial Statements, Captions [Line Items]
Total revenues	$ 115,065	$ 113,971	$ 116,508	$ 126,640	$ 118,080	$ 114,846	$ 117,132	$ 126,037		$ 472,184	$ 476,095	$ 355,561
Operating expenses:
Cost of revenues (excluding amortization of internal use software)	39,533	33,886	36,143	45,242	43,223	39,031	43,319	48,088		154,804	173,661	129,046
Technology and development, sales and marketing, general and administrative, and employee termination and other charges	59,802	61,454	53,664	56,620	49,547	50,365	48,619	45,581
Amortization and impairment	10,772	10,502	10,191	9,991	9,858	9,402	9,393	9,237	$ 3,700	41,456	37,890	37,175
Total operating expenses	110,107	105,842	99,998	111,853	102,628	98,798	101,331	102,906		427,800	405,663	329,494
Income from operations	4,958	8,129	16,510	14,787	15,452	16,048	15,801	23,131		44,384	70,432	26,067
Other, net	(1,317)	(1,071)	(965)	(916)	(1,443)	(1,749)	(1,680)	(1,590)
Income before income taxes	3,641	7,058	15,545	13,871	14,009	14,299	14,121	21,541		40,115	63,970	24,831
Income tax (provision) benefit	(1,738)	(4,934)	(4,621)	(2,852)	(5,020)	(5,236)	6,157	(5,484)		(14,145)	(9,583)	(8,929)
Net income	$ 1,903	$ 2,124	$ 10,924	$ 11,019	$ 8,989	$ 9,063	$ 20,278	$ 16,057		$ 25,970	$ 54,387	$ 15,902
Net income per share:
Basic (in dollars per share)	$ 0.05	$ 0.05	$ 0.27	$ 0.28	$ 0.23	$ 0.23	$ 0.54	$ 0.43		$ 0.65	$ 1.41	$ 0.44
Diluted (in dollars per share)	$ 0.05	$ 0.05	$ 0.27	$ 0.27	$ 0.23	$ 0.23	$ 0.53	$ 0.42		$ 0.64	$ 1.38	$ 0.43
Shares used in computing net income per share:
Basic (in shares)	39,853	39,853	39,853	39,823	38,447	39,641	37,419	37,025		39,846	38,447	36,404
Diluted (in shares)	40,340	40,492	40,412	40,480	39,415	40,264	38,613	38,441		40,434	39,415	37,210
Healthcare
Condensed Financial Statements, Captions [Line Items]
Total revenues	$ 65,376	$ 66,125	$ 68,104	$ 75,256	$ 66,046	$ 65,893	$ 68,202	$ 74,674		$ 274,861	$ 274,815	$ 195,108
COBRA
Condensed Financial Statements, Captions [Line Items]
Total revenues	26,045	25,081	26,200	28,835	29,142	26,897	27,018	28,550		106,161	111,607	73,765
Commuter
Condensed Financial Statements, Captions [Line Items]
Total revenues	19,426	18,785	18,847	18,878	18,508	17,987	17,836	18,543		75,936	72,874	70,215
Other
Condensed Financial Statements, Captions [Line Items]
Total revenues	$ 4,218	$ 3,980	$ 3,357	$ 3,671	$ 4,384	$ 4,069	$ 4,076	$ 4,270		$ 15,226	$ 16,799	$ 16,473