Description of Business and Summary of Significant Accounting Policies Impact of adopting Topic 606 on the Company’s unaudited consolidated financial statements (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Operating revenue	$ 108,230	$ 79,103
Cost of services provided	39,591	25,187
Operating Expenses	74,334	53,413
Operating Income (Loss)	33,896	25,690
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	28,582	27,492
Income tax expense	2,126	869
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	26,456	26,623
Net Income (Loss) Attributable to Parent	$ 26,208	$ 26,427
Basic earnings per common share	$ 0.83	$ 0.83
Diluted earnings per common share	$ 0.83	$ 0.83
Other current assets	$ 30,533		$ 33,532
Assets, Current	290,867		252,932
Deferred tax asset, net	48,489		43,529
Other assets	15,889		11,720
Assets	1,162,444		1,113,013
Deferred Revenue, Current	27,492		22,562
Liabilities, Current	158,675		146,932
Deferred Revenue, Noncurrent	8,822		1,423
Liabilities	621,517		579,254
Retained Earnings (Accumulated Deficit)	523,668		510,975
Increase (Decrease) in Other Operating Assets	554	$ (198)
Deferred revenue	(2,361)	382
Net Cash Provided by (Used in) Operating Activities	25,493	$ 15,787
Accounting Standards Update 2014-09 Adjustments
Operating revenue	(623)
Cost of services provided	(139)
Operating Expenses	(139)
Operating Income (Loss)	(484)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(484)
Income tax expense	(118)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(366)
Net Income (Loss) Attributable to Parent	$ (366)
Basic earnings per common share	$ (0.01)
Diluted earnings per common share	$ (0.01)
Other current assets	$ (870)		898
Assets, Current	(870)		898
Deferred tax asset, net	(2,843)		2,843
Other assets	(1,392)		1,502
Assets	(5,105)		5,243
Deferred Revenue, Current	(4,787)		5,124
Liabilities, Current	(4,787)		5,124
Deferred Revenue, Noncurrent	(7,565)		8,921
Liabilities	(12,352)		14,045
Retained Earnings (Accumulated Deficit)	7,247		$ (8,802)
Increase (Decrease) in Other Operating Assets	139
Deferred revenue	1,693
Net Cash Provided by (Used in) Operating Activities	1,188
Balances without Adoption of ASC 606
Operating revenue	107,607
Cost of services provided	39,452
Operating Expenses	74,195
Operating Income (Loss)	33,412
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	28,098
Income tax expense	2,008
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	26,090
Net Income (Loss) Attributable to Parent	$ 25,842
Basic earnings per common share	$ 0.82
Diluted earnings per common share	$ 0.82
Other current assets	$ 29,663
Assets, Current	289,997
Deferred tax asset, net	45,646
Other assets	14,497
Assets	1,157,339
Deferred Revenue, Current	22,705
Liabilities, Current	153,888
Deferred Revenue, Noncurrent	1,257
Liabilities	609,165
Retained Earnings (Accumulated Deficit)	530,915
Increase (Decrease) in Other Operating Assets	693
Deferred revenue	(668)
Net Cash Provided by (Used in) Operating Activities	$ 26,681