Fair Value Measurements (Narrative) (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Goodwill impairment charges	$ 65,108	$ 0	$ 151,108	$ 391,000
Money market funds | Restricted cash and cash equivalents
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Settlement funds	$ 67,100		$ 67,100		$ 86,900
Discount rate | Minimum
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discount rate applied	0.095		0.095
Discount rate | Maximum
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discount rate applied	0.150		0.150
Discount rate | Weighted average
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Discount rate applied	0.114		0.114