Commitments and Contingencies - Lease and Other Commitments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Contingencies - Legal Matters
Maximum separation payments payable for early termination of employment arrangements without cause	$ 4,900
Obligation to purchase market data, maintenance and other services	58,300
Rent expense	12,700	$ 12,400	$ 12,400
Minimum future rental commitments under non-cancelable operating leases
2017	12,540
2018	12,282
2019	11,256
2020	9,775
2021	9,789
2022 and thereafter	67,580
Total	$ 123,222