Industry Segments and Geographic Information Industry Segments and Geographic Information 2 (Details) - USD ($) $ 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
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 257,590	$ 305,144	$ 316,319	$ 251,092	$ 315,850	$ 306,371	$ 242,489	$ 212,857	$ 1,130,145	$ 1,077,567	$ 909,398
Transfers between geographic areas									(1,252)	(2,871)	(112)
Identifiable assets	1,656,376				2,082,388				1,656,376	2,082,388	1,206,533
UNITED STATES
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									896,131	768,688	673,376
Transfers between geographic areas									0	0	0
Identifiable assets	1,427,481				1,778,357				1,427,481	1,778,357	852,483
Canada and Mexico [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									44,542	73,632	58,080
Transfers between geographic areas									0	0	0
Identifiable assets	72,007				97,737				72,007	97,737	104,831
South America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									26,554	40,719	31,788
Transfers between geographic areas									0	0	0
Identifiable assets	25,035				32,267				25,035	32,267	43,326
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									80,432	105,457	102,990
Transfers between geographic areas									1,252	2,871	112
Identifiable assets	64,695				94,209				64,695	94,209	150,415
Africa [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									20,761	22,277	15,127
Transfers between geographic areas									0	0	0
Identifiable assets	7,541				7,895				7,541	7,895	9,063
Asia and other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									61,725	66,794	28,037
Transfers between geographic areas									0	0	0
Identifiable assets	59,617				71,923				59,617	71,923	46,351
Eliminations [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Identifiable assets	$ 0				$ 0				$ 0	$ 0	$ 64