Quarterly Financial Data - Summary of Quarterly Results (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Revenues, net	$ 165,858	$ 163,503	$ 155,621	$ 143,510	$ 135,286	$ 122,457	$ 119,738	$ 121,797	$ 628,492	$ 499,278	$ 478,452
Total Gross profit	59,742	60,305	55,143	50,385	43,915	37,474	38,479	46,875	225,575	166,743	187,510
Net income	$ 14,762	$ 15,162	$ 12,074	$ 9,567	$ 7,461	$ 6,075	$ 7,762	$ 11,147	$ 51,565	$ 32,445	$ 48,097
Earnings Per Share:
Basic (in dollars per share)	$ 0.44	$ 0.46	$ 0.36	$ 0.29	$ 0.23	$ 0.18	$ 0.24	$ 0.34	$ 1.55	$ 0.99	$ 1.47
Diluted (in dollars per share)	$ 0.43	$ 0.44	$ 0.35	$ 0.28	$ 0.22	$ 0.18	$ 0.23	$ 0.33	$ 1.51	$ 0.96	$ 1.42
Weighted-average number of shares used in computing earnings per share:
Basic (in shares)	33,231,716	33,307,312	33,417,079	33,236,259	32,986,276	32,890,475	32,812,155	32,523,490	33,298,104	32,804,606	32,750,178
Diluted (in shares)	34,272,731	34,180,635	34,207,973	34,051,971	33,761,462	33,676,665	33,673,669	33,428,544	34,178,340	33,636,593	33,842,938
Note:
Stock compensation expense	$ 3,768	$ 4,471	$ 3,553	$ 4,255	$ 2,493	$ 2,376	$ 1,966	$ 4,176	$ 16,047	$ 11,011	$ 11,832
Amortization of intangibles	2,717	2,642	2,808	2,059	2,157	1,441	1,489	1,536	10,226	6,623	6,300
Operations Management
Segment Reporting Information [Line Items]
Revenues, net	129,397	128,043	125,048	123,853	116,292	104,511	104,614	108,246	506,341	433,663	432,916
Total Gross profit	47,333	46,566	44,239	44,124	38,075	32,651	34,151	42,293	182,262	147,170	172,675
Analytics
Segment Reporting Information [Line Items]
Revenues, net	36,461	35,460	30,573	19,657	18,994	17,946	15,124	13,551	122,151	65,615	45,536
Total Gross profit	$ 12,409	$ 13,739	$ 10,904	$ 6,261	$ 5,840	$ 4,823	$ 4,328	$ 4,582	$ 43,313	$ 19,573	$ 14,835