Derivative Instruments (Schedule Of Estimated Amount Of Net Gains Associated With Derivatives) (Details) $ in Millions	Dec. 31, 2015 USD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Net unrealized gains to be reclassified to contract drilling expense	$ (11.2)
Net realized gains to be reclassified to depreciation expense	0.9
Net realized (losses) to be reclassified to interest expense	(0.4)
Net gains to be reclassified to earnings	$ (10.7)