Arrangements With Off-Balance Sheet Risk (Narrative) (Details) $ in Millions	1 Months Ended		225 Months Ended
	Dec. 31, 2011 USD ($)	Jun. 30, 2011 USD ($)	Dec. 31, 2036	Mar. 31, 2018 USD ($) satellites	Dec. 31, 2017 USD ($)
Guarantees [Line Items]
Number of satellite missions | satellites				4
Additional potentially unrecoverable deferred production costs	$ 114	$ 271
ULA [Member]
Guarantees [Line Items]
Delta launch program inventories included in contributed assets				$ 1,360
Delta launch program inventories subject to inventory supply agreement				1,860
Contributed Delta launch program inventories consumed by ULA				1,293
Revenues and cost of sales recorded under inventory supply agreement				1,545
Payments received under inventory supply agreement				1,740
Payments made under inventory supply agreement				48
Contributed Delta Program Launch Inventory [Member] | ULA [Member]
Guarantees [Line Items]
Maximum Potential Payments				67	$ 72
Contract Pricing [Member] | ULA [Member]
Guarantees [Line Items]
Maximum Potential Payments				261	261
Carrying Amount of Liabilities				$ 7	7
Indemnification Agreement [Member]
Guarantees [Line Items]
Number of satellite missions | satellites				3
Other Delta Contracts [Member] | Deferred support costs [Member]
Guarantees [Line Items]
Maximum Potential Payments				$ 85
Other Delta Contracts [Member] | Deferred production costs [Member]
Guarantees [Line Items]
Maximum Potential Payments				91
Other Delta Contracts [Member] | ULA [Member]
Guarantees [Line Items]
Maximum Potential Payments				191	191
Carrying Amount of Liabilities
Deferred Support and Production Costs [Member]
Guarantees [Line Items]
Loss Contingency, Estimate of Possible Loss				317
Credit Guarantee [Member]
Guarantees [Line Items]
Maximum Potential Payments				117	109
Carrying Amount of Liabilities				13	$ 16
Guarantor Obligations, Term			2036
Maximum [Member] | Indemnification Agreement [Member]
Guarantees [Line Items]
Loss Contingency, Estimate of Possible Loss				$ 280