Fair Value Measurements (Details 2) (Level 3, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of year	$ 2	$ 2	$ 3
Issuance of guarantees	2	2	4
Expiration of guarantees	(3)	(2)	(5)
Balance at end of year	$ 1	$ 2	$ 2