Industry Segments and Geographic Information Industry Segments and Geographic Information 2 (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	$ 173,222	$ 176,553	$ 175,660	$ 169,329	$ 257,590	$ 305,144	$ 316,319	$ 251,092	$ 694,764	$ 1,130,145	$ 1,077,567
Transfers between geographic areas									(93)	(1,252)	(2,871)
Identifiable assets	1,315,540				1,636,202				1,315,540	1,636,202	2,063,522
UNITED STATES
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									535,613	896,131	768,688
Transfers between geographic areas									0	0	0
Identifiable assets	1,132,986				1,403,916				1,132,986	1,403,916	1,759,491
Canada and Mexico [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									34,560	44,542	73,632
Transfers between geographic areas									0	0	0
Identifiable assets	64,163				74,260				64,163	74,260	97,737
South America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									20,480	26,554	40,719
Transfers between geographic areas									0	0	0
Identifiable assets	21,354				25,603				21,354	25,603	32,267
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									71,882	80,432	105,457
Transfers between geographic areas									93	1,252	2,871
Identifiable assets	53,713				64,695				53,713	64,695	94,209
Africa [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									10,345	20,761	22,277
Transfers between geographic areas									0	0	0
Identifiable assets	5,711				7,542				5,711	7,542	7,895
Asia and other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									21,884	61,725	66,794
Transfers between geographic areas									0	0	0
Identifiable assets	37,613				60,186				37,613	60,186	71,923
Eliminations [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Identifiable assets	$ 0				$ 0				$ 0	$ 0	$ 0