Intangible Assets (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense of intangible assets	$ 2	$ 2	$ 4	$ 4