Basis Of Presentation And New Accounting Standards (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Jan. 01, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Assets
Unbilled and other		$ 76,914		$ 76,914		$ 29,947
Other current assets		51,519		51,519		41,768
Liabilities
Accrued liabilities		81,087		81,087		71,680
Deferred tax liabilities		106,560		106,560		103,349
Equity
Retained earnings		369,659		369,659		$ 352,906
Statement of Operations
Net revenues		204,625	$ 150,329	368,887	$ 254,857
Income from operations		24,772	5,050	23,656	(12,655)
Income before income taxes		18,082	(1,380)	15,609	(22,396)
Income tax provision		298	5,023	385	422
Net income		17,784	$ (6,403)	15,224	$ (22,818)
Pro Forma Without Adoption of ASC 606
Assets
Unbilled and other		76,814		76,814
Other current assets		50,792		50,792
Liabilities
Accrued liabilities		81,618		81,618
Deferred tax liabilities		106,275		106,275
Equity
Retained earnings		368,586		368,586
Statement of Operations
Net revenues		203,267		367,529
Income from operations		23,414		22,298
Income before income taxes		16,724		14,251
Income tax provision		13		100
Net income		16,711		14,151
Effect of Change | ASC 606
Assets
Unbilled and other		100		100
Other current assets		727		727
Liabilities
Accrued liabilities		(531)		(531)
Deferred tax liabilities		285		285
Equity
Retained earnings		1,073		1,073
Statement of Operations
Net revenues		1,358		1,358
Income from operations		1,358		1,358
Income before income taxes		1,358		1,358
Income tax provision		285		285
Net income		$ 1,073		$ 1,073
Accumulated OCI | ASU No. 2018-02
Statement of Operations
Reclassification of net stranded tax benefits	$ (1,500)
Retained Earnings | ASU No. 2018-02
Statement of Operations
Reclassification of net stranded tax benefits	$ 1,500