Segment Information (Schedule Of Revenues By Geographic Segment) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 354,418	$ 326,225	$ 356,271	$ 413,133	$ 545,150	$ 601,396	$ 710,784	$ 917,235	$ 1,450,047	$ 2,774,565	$ 4,556,622
Long-lived assets	1,605,365				2,123,291				1,605,365	2,123,291
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									1,080,513	2,185,071	3,848,929
Long-lived assets	1,288,077				1,799,418				1,288,077	1,799,418
Other Countries [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									369,534	589,494	$ 707,693
Long-lived assets	$ 317,288				$ 323,873				$ 317,288	$ 323,873