Income Taxes (Details 3) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Deferred tax assets:
General business credits	$ 2,186	$ 277
Impairment losses on investments	291	318
License fees capitalized for tax purposes	61,770	75,181
Nonqualified stock options	42,697	40,808
SERP	17,478	14,059
STAP awards	86,414	84,274
Other	29,086us-gaap_DeferredTaxAssetsOther	28,118us-gaap_DeferredTaxAssetsOther
Total deferred tax assets	239,922us-gaap_DeferredTaxAssetsGross	243,035us-gaap_DeferredTaxAssetsGross
Deferred tax liabilities:
Plant and equipment principally due to differences in depreciation	(30,758)	(32,725)
Other	(7,854)us-gaap_DeferredTaxLiabilitiesOther	(1,351)us-gaap_DeferredTaxLiabilitiesOther
Net deferred tax asset before valuation allowance	201,310	208,959
Valuation allowance	(2,981)	(2,507)
Net deferred tax assets	$ 198,329us-gaap_DeferredTaxAssetsLiabilitiesNet	$ 206,452us-gaap_DeferredTaxAssetsLiabilitiesNet

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