Summary of Significant Accounting Policies (Government Contracts) (Details) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Aug. 15, 2012	Apr. 01, 2011 options
Significant Accounting Policies [Line Items]
Contracts revenue	$ 603,975,000	$ 572,266,000	$ 689,121,000
Government Contracts [Member] | T-3 Contract [Member]
Significant Accounting Policies [Line Items]
Number of administrative services option periods					5
Deferred costs					43,800,000
Deferred revenue					52,500,000
Costs paid and reimbursable	2,500,000,000	2,500,000,000	2,600,000,000
Government Contracts [Member] | MFLC Contract [Member]
Significant Accounting Policies [Line Items]
Effective date of contract	August 15, 2012
Administrative services option period				5 years
Contracts revenue	119,700,000	104,800,000	221,300,000
Government Contracts [Member] | PC3 [Member]
Significant Accounting Policies [Line Items]
Deferred revenue	68,200,000
Contracts revenue	$ 24,700,000