Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Tables) (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Deferrec Revenue and costs [Line Items]
Net Income (Loss) Attributable to Parent	$ 24,717,000	$ 40,647,000	$ 41,662,000	$ 30,485,000	$ (58,051,000)	$ 34,037,000	$ 34,320,000	$ 35,245,000	$ 137,511,000	$ 45,551,000	$ 95,405,000
Amortization of Intangible Assets									20,934,000	22,731,000	13,391,000
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	(314,498,000)				(274,463,000)				(314,498,000)	(274,463,000)
Deferred Equipment Revenue	811,000				735,000				811,000	735,000
Deferred Fixed Priced Support Or Maintenance Contract Revenue	3,854,000				3,383,000				3,854,000	3,383,000
Other Deferred Revenue	6,578,000				6,828,000				6,578,000	6,828,000
Total deferred revenue	11,243,000				10,946,000				11,243,000	10,946,000
Deferred Revenue, Current	11,190,000				10,811,000				11,190,000	10,811,000
Deferred Revenue, Noncurrent	53,000				135,000				53,000	135,000
Deferred Costs, Current	502,000				709,000				502,000	709,000
Deferred Costs, Noncurrent	698,000				1,099,000				698,000	1,099,000
Deferred Costs	$ 1,200,000				$ 1,808,000				$ 1,200,000	$ 1,808,000