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		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Impact of adopting Topic 606 on the Company’s unaudited consolidated financial statements [Abstract]
Operating revenue	$ 144,275	$ 124,626	$ 287,199	$ 232,856
Cost of Goods and Services Sold	50,954	43,559	96,883	83,150
Operating Expenses	102,993	86,311	191,786	160,645
Operating Income (Loss)	41,282	38,315	95,413	72,211
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	29,350	31,293	53,309	59,875
Income tax expense	(1,004)	(2,222)	80	(4,348)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	28,346	29,071	53,389	55,527
Net Income (Loss) Attributable to Parent	$ 28,851	$ 29,180	$ 54,561	$ 55,388
Basic earnings per common share	$ 0.95	$ 0.93	$ 1.79	$ 1.76
Diluted earnings per common share	$ 0.94	$ 0.92	$ 1.78	$ 1.75
Other current assets	$ 60,747		$ 60,747		$ 59,274
Assets, Current	370,174		370,174		427,380
Deferred tax asset, net	60,135		60,135		54,629
Other assets	48,344		48,344		26,714
Assets	1,622,503		1,622,503		1,610,947
Deferred Revenue, Current	30,369		30,369		35,609
Liabilities, Current	272,432		272,432		317,428
Deferred Revenue, Noncurrent	8,161		8,161		9,051
Liabilities	1,034,950		1,034,950		1,066,510
Retained Earnings (Accumulated Deficit)	$ 582,913		582,913		$ 535,118
Increase (Decrease) in Other Operating Assets			758	$ 40
Deferred revenue			(6,192)	(5,544)
Net Cash Provided by (Used in) Operating Activities			$ 38,242	$ 39,893