Cash and Investments - Additional Durational Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended	3 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Clearwire Corporation
Cash, cash equivalents and marketable securities [Line Items]
Gross realized gains on the sale of our marketable securities	$ 381	$ 212
Gross realized losses on the sale of our marketable securities	127	27
Other-than-temporary impairment charge on investment	$ 110	$ 0	$ 0	$ 88

The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

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