Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Operating Loss Carryforwards [Line Items]
Effective tax rate (as a percent)	16.80%	13.50%	13.80%	16.40%
Benefits Tax Planning and Completion of Audits	$ 18
Maximum period for recognizing capital losses			5 years
Valuation Allowance	6		6		6
Gross unrecognized tax benefits	153		153		144
Unrecognized tax benefits, net of federal tax benefits that would affect the effective tax rate if recognized	5		5		23
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Estimated Range of Change, Lower Bound	140		140
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Estimated Range of Change, Upper Bound	150		150
Net increase (decrease) in interest and penalties	2	1	1	3
Payable (receivable) related to accrued interest and penalties	37		37		36
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	$ 6		$ 6