Statement of Cash Flow Information - Non-Cash Additions and Non-Cash Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Nonmonetary Transaction
Non-monetary exchanges related to resale licensing revenue			$ 0	$ 1,250
Non-cash revenue			97	1,407
Acquisition revenue on underwriting [Member]
Nonmonetary Transaction
Non-cash revenue	$ 0	$ 87	0	126
Licensing revenue from specific data licenses and selections [Member]
Nonmonetary Transaction
Non-cash revenue	63	1,000	63	1,250
Solutions and other revenue recognized [Member]
Nonmonetary Transaction
Non-cash revenue	$ 29	$ 31	$ 34	$ 31