Commitments And Contingencies (Narrative) (Details)		3 Months Ended			9 Months Ended
	Aug. 07, 2018	Sep. 30, 2018 USD ($)	Sep. 06, 2018 lawsuit	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Feb. 08, 2018 USD ($)
Debt Instrument [Line Items]
Capital leases, future minimum payments due		$ 500,000			$ 500,000
Operating leases expiration year					2028
Contractual sublease income		8,700,000			$ 8,700,000
Rent expense		1,900,000		$ 1,900,000	5,900,000	$ 5,800,000
Sublease income		$ 500,000		$ 468,000.000	$ 1,400,000	$ 1,249,000.000
Term in which consolidated amended complaint must be filed following restatement	45 days
Number of derivative lawsuits | lawsuit			2
Term needed to notify court of dismissal of Securities Class Action, denial of defendants' motions to dismiss, party giving notice to vacate stay	15 days
OPM Claims Denial | Positive Outcome of Litigation
Debt Instrument [Line Items]
Gain contingency, unrecorded amount							$ 9,100,000