Commitments and Contingencies (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Jun. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Commitments and Contingencies
Rent expense			$ 12,400	$ 12,400	$ 17,600
Duplicate rent charges		$ 2,600			$ 2,600
Charge recorded for remaining rent expense at the entity's old headquarters upon completion of the move	$ 2,300
Minimum future rental commitments under non-cancelable operating leases
2016			16,916
2017			12,271
2018			11,035
2019			9,519
2020			8,447
2021 and thereafter			67,711
Total			125,899
Other Commitments
Maximum separation payments payable for early termination of employment arrangements without cause			5,500
Obligation to purchase market data, maintenance and other services			$ 40,800