Organization and Significant Accounting Policies - Impact of ASC 606 (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
Consolidated Statement of Operations
Revenues	$ 43,256	$ 42,476	$ 40,628	$ 43,114	$ 43,770	$ 43,636	$ 42,325	$ 41,444	$ 169,474	$ 171,175	$ 179,561
Selling and marketing									24,553	22,823	24,768
Consolidated Statements of Comprehensive Income
Foreign currency translation adjustments									(49)	11	(109)
Consolidated Balance Sheets
Accounts receivable, net	32,386				29,722				32,386	29,722
Prepaid expenses and other	9,578				5,752				9,578	5,752
Deferred revenue	26,285				28,857				26,285	28,857
Deferred revenue	476				1,063				476	1,063
Accumulated other comprehensive loss	(1,301)				(1,088)				(1,301)	(1,088)
Retained earnings	185,294				191,796				185,294	191,796
Calculated under Revenue Guidance in Effect before Topic 606
Consolidated Statements of Comprehensive Income
Foreign currency translation adjustments									117	11	(109)
Consolidated Balance Sheets
Accounts receivable, net	30,709				29,722				30,709	29,722
Prepaid expenses and other	9,192				5,752				9,192	5,752
Deferred revenue	32,267				28,857				32,267	28,857
Deferred revenue	624				1,063				624	1,063
Accumulated other comprehensive loss	(1,015)				(1,088)				(1,015)	(1,088)
Retained earnings	$ 176,815				$ 191,796				176,815	191,796
Software Operations
Consolidated Statement of Operations
Revenues									75,197	69,987	69,971
Selling and marketing									24,553
Software Operations | Calculated under Revenue Guidance in Effect before Topic 606
Consolidated Statement of Operations
Revenues									73,265	69,987	69,971
Selling and marketing									$ 24,250	$ 22,823	$ 24,768