Fair Value Of Financial Instruments (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Contingent interest payment for debenture	$ 0	$ 0	$ (6,544)	$ (5,225)
Interest Payable	6,800		$ 6,800
Fair value assumptions expected volatility rate			26.00%
fair value assumptions credit spread			6.00%
Convertible Debt, Fair Value Disclosures	3,100,000		$ 3,100,000
Debt instrument fair value senior notes 2023	761,300		761,300
Debt instrument fair value senior notes 2025	$ 512,800		$ 512,800
Minimum [Member]
fair value hypothetical increase decrease in volatility rate			21.00%
fair value hypothetical increase decrease in credit spread			5.00%
Maximum [Member]
fair value hypothetical increase decrease in volatility rate			31.00%
fair value hypothetical increase decrease in credit spread			7.00%