Unaudited Quarterly Consolidated Financial Information (Schedule Of Unaudited Quarterly Consolidated Financial Information) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Unaudited Quarterly Consolidated Financial Information [Abstract]
Revenues	$ 208,678	$ 274,088	$ 345,671	$ 262,193	$ 206,473	$ 302,401	$ 376,920	$ 312,429	$ 1,090,630	$ 1,198,223	$ 1,192,680
Gross profit	72,744	120,821	189,870	127,370	76,530	155,017	202,571	156,227	510,805	590,345	623,198
Restructuring	1,274	981	2,810	3,663	6,637	7,585	4,060	2,250	8,728	20,532
Asset impairment charges	7,771	5,460	2,075		2,997	2,600	3,230		15,306	8,827	10,949
Income (loss) from operations	(65,581)	(20,730)	16,349	(2,362)	(64,572)	1,113	41,911	16,822	(72,324)	(4,726)	63,095
Net income (loss)	(70,173)	(24,024)	13,426	(2,425)	(53,094)	15,767	23,277	9,124	(83,196)	(4,926)	10,420
Net income (loss) attributable to common stockholders	$ (73,942)	$ (27,776)	$ 9,690	$ (5,979)	$ (56,867)	$ 12,009	$ 19,523	$ 6,373	$ (98,007)	$ (18,962)	$ 10,420
Basic income (loss) per common share	$ (1.01)	$ (0.37)	$ 0.11	$ (0.08)	$ (0.70)	$ 0.12	$ 0.19	$ 0.06	$ (1.30)	$ (0.22)	$ 0.12
Diluted income (loss) per common share	$ (1.01)	$ (0.37)	$ 0.11	$ (0.08)	$ (0.70)	$ 0.12	$ 0.19	$ 0.06	$ (1.30)	$ (0.22)	$ 0.12