Derivatives and Hedging (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014
6.00% Senior Notes due March 2018
Derivatives and Hedging
Interest rate on notes hedged to reduce exposure to changes in fair value (as a percent)	6.00%
6.50% Senior Notes due November 2020
Derivatives and Hedging
Interest rate on notes hedged to reduce exposure to changes in fair value (as a percent)	6.50%
Derivatives designated as hedging instruments | Interest rate swaps | Fair value hedges | Other assets
Derivatives and Hedging
Derivatives at fair value	$ 6
Derivatives designated as hedging instruments | Interest rate swaps | Fair value hedges | Pay
Derivatives and Hedging
Aggregate notional amount	1,050
Weighted average variable rate (as a percent)	4.71%
Derivatives designated as hedging instruments | Interest rate swaps | Fair value hedges | Receive
Derivatives and Hedging
Aggregate notional amount	$ 1,050
Weighted average fixed rate (as a percent)	6.14%