Summary of Significant Accounting Policies (Details) (USD $)	3 Months Ended			3 Months Ended	1 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 Common equity securities of Sprint	Mar. 31, 2013 Common equity securities of Sprint Other current assets	Apr. 30, 2013 Subsequent event Common equity securities of Sprint	May 01, 2013 Subsequent event Common equity securities of Sprint
Derivative Financial Instruments
Aggregate notional amount			$ 341,000,000			$ 592,000,000
Fair value of derivative financial instruments				209,000,000
Equity securities			75,000,000
Prepayments applied to purchase derivative assets					209,000,000
Incremental funds used to purchase derivative assets					42,000,000
Aggregate additional purchases					251,000,000
Unrealized gain on derivative financial instruments	8,358,000			8,000,000
Advertising Costs
Advertising costs	$ 122,000,000	$ 99,000,000