Export Sales and Major Customers (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 375,401	$ 321,976	$ 333,081	$ 334,813	$ 354,589	$ 372,882	$ 371,268	$ 338,030	$ 1,365,271	$ 1,436,769	$ 1,345,923
U.S. Government and its agencies and subcontracts with the U.S. Government's prime contractors [Member]
Revenue, Major Customer [Line Items]
Revenue from major customer, percentage (in hundredths)									83.00%	79.00%	71.00%
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									1,225,217	1,155,003	1,035,090
Europe and Eurasia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									91,838	150,746	146,623
Mexico and South America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									8,071	96,147	131,240
East Asia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									$ 40,145	$ 34,873	$ 32,970