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, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Operating revenue	$ 124,626	$ 87,387	$ 232,856	$ 166,490
Cost of Goods and Services Sold	43,559	30,932	83,150	56,119
Operating Expenses	86,311	60,848	160,645	114,261
Operating Income (Loss)	38,315	26,539	72,211	52,229
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	31,293	23,595	59,875	51,087
Income tax expense	(2,222)	302	(4,348)	(567)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	29,071	23,897	55,527	50,520
Net Income (Loss) Attributable to Parent	$ 29,180	$ 23,434	$ 55,388	$ 49,861
Basic earnings per common share	$ 0.93	$ 0.74	$ 1.76	$ 1.58
Diluted earnings per common share	$ 0.92	$ 0.74	$ 1.75	$ 1.57
Other current assets	$ 33,205		$ 33,205		$ 33,532
Assets, Current	328,229		328,229		252,932
Deferred tax asset, net	46,819		46,819		43,529
Other assets	22,710		22,710		11,720
Assets	1,357,577		1,357,577		1,113,013
Deferred Revenue, Current	31,011		31,011		22,562
Liabilities, Current	194,077		194,077		146,932
Deferred Revenue, Noncurrent	7,152		7,152		1,423
Liabilities	809,675		809,675		579,254
Retained Earnings (Accumulated Deficit)	550,480		550,480		510,975
Increase (Decrease) in Other Operating Assets			40	$ (487)
Deferred revenue			(5,544)	(1,622)
Net Cash Provided by (Used in) Operating Activities			39,893	$ 31,232
Accounting Standards Update 2014-09 Adjustments
Operating revenue	(1)		(624)
Cost of Goods and Services Sold	19		(120)
Operating Expenses	19		(120)
Operating Income (Loss)	(20)		(504)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(20)		(504)
Income tax expense	5		123
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(15)		(381)
Net Income (Loss) Attributable to Parent	$ (15)		$ (381)
Basic earnings per common share	$ 0.00		$ (0.01)
Diluted earnings per common share	$ 0.00		$ (0.01)
Other current assets	$ (848)		$ (848)		898
Assets, Current	(848)		(848)		898
Deferred tax asset, net	(2,309)		(2,309)		2,843
Other assets	(1,312)		(1,312)		1,502
Assets	(4,469)		(4,469)		5,243
Deferred Revenue, Current	(4,618)		(4,618)		5,124
Liabilities, Current	(4,618)		(4,618)		5,124
Deferred Revenue, Noncurrent	(6,951)		(6,951)		8,921
Liabilities	(11,569)		(11,569)		14,045
Retained Earnings (Accumulated Deficit)	7,100		7,100		$ (8,802)
Increase (Decrease) in Other Operating Assets			120
Deferred revenue			2,476
Net Cash Provided by (Used in) Operating Activities			1,975
Balances without Adoption of ASC 606
Operating revenue	124,625		232,232
Cost of Goods and Services Sold	43,578		83,030
Operating Expenses	86,330		160,525
Operating Income (Loss)	38,295		71,707
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	31,273		59,371
Income tax expense	(2,217)		(4,225)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	29,056		55,146
Net Income (Loss) Attributable to Parent	$ 29,165		$ 55,007
Basic earnings per common share	$ 0.93		$ 1.75
Diluted earnings per common share	$ 0.92		$ 1.74
Other current assets	$ 32,357		$ 32,357
Assets, Current	327,381		327,381
Deferred tax asset, net	44,510		44,510
Other assets	21,398		21,398
Assets	1,353,108		1,353,108
Deferred Revenue, Current	26,393		26,393
Liabilities, Current	189,459		189,459
Deferred Revenue, Noncurrent	201		201
Liabilities	798,106		798,106
Retained Earnings (Accumulated Deficit)	$ 557,580		557,580
Increase (Decrease) in Other Operating Assets			160
Deferred revenue			(3,068)
Net Cash Provided by (Used in) Operating Activities			$ 41,868