Contingencies - Narrative (Details) £ in Millions		1 Months Ended
	Jan. 18, 2017 USD ($)	Jan. 31, 2014 USD ($)	Jan. 31, 2014 GBP (£)	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)
Loss Contingencies [Line Items]
Legal reserves				$ 45,000,000
Unrecognized tax benefits				63,000,000	$ 71,000,000
Minimum
Loss Contingencies [Line Items]
Estimate of possible loss				0
Maximum
Loss Contingencies [Line Items]
Estimate of possible loss				15,000,000
GovEx Inquiry
Loss Contingencies [Line Items]
Litigation reserve				3,000,000
Legal Reserve | Invoicing Matter
Loss Contingencies [Line Items]
Legal reserves				32,000,000
Estimate of possible loss				340,000,000
Regulatory Matter | Transition Management
Loss Contingencies [Line Items]
Legal reserves				$ 32,300,000
U.K. FCA | Regulatory Matter | Transition Management
Loss Contingencies [Line Items]
Settlement, amount		$ 37,800,000	£ 22.9
Department of Justice | Regulatory Matter | Transition Management
Loss Contingencies [Line Items]
Settlement, amount	$ 32,300,000
SEC | Regulatory Matter | Transition Management
Loss Contingencies [Line Items]
Settlement, amount	$ 32,300,000