Goodwill and Other Intangible Assets - Estimated Aggregate Pre-Tax Amortization Expense Related to Intangible Assets (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense remainder of 2013	$ 65
Amortization expense 2014	50
Amortization expense 2015	23
Amortization expense 2016	21
Amortization expense 2017	$ 18