Basis of Presentation and Summary of Significant Accounting Policies Basis of Presentation and Summary of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended			1 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2013
Long Lived Assets Held-for-sale [Line Items]
Gain on sale of intangible assets	$ 0	$ 32	$ 0
Wireless spectrum licenses
Long Lived Assets Held-for-sale [Line Items]
Disposal group, including discontinued operation, intangible assets, current				43
Gain on sale of intangible assets				$ 32