Business Segments (Schedule of Revenue and Long-Lived Assets, By Geographical Area) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Consolidated revenue	$ 5,559	$ 6,395	$ 5,708	$ 6,263	$ 5,610	$ 6,217	$ 5,393	$ 5,536	$ 23,925	$ 22,756	$ 17,912
Consolidated long-lived assets	83,167				81,362				83,167	81,362	81,611
U.S. [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Consolidated revenue									22,508	21,211	16,366
Consolidated long-lived assets	80,709				78,581				80,709	78,581	79,144
Latin America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Consolidated revenue									1,417	1,545	1,546
Consolidated long-lived assets	$ 2,458				$ 2,781				$ 2,458	$ 2,781	$ 2,467