Employee Benefit Plans (Reconciliations of Plan assets and the Projected Benefit Obligation, the Weighted-Average Assumptions Used to Determine Year-End Benefit Obligations, and the Amounts Recognized in Accumulated Other Comprehensive Income (Loss) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Fair value of plan assets at December 31	$ 2,028,000,000		$ 1,953,000,000
Defined Benefit Pension Plans | Qualified Plan
Fair value of plan assets at January 1	1,955,000,000		1,508,000,000
Actual return on plan assets	136,000,000		199,000,000		92,000,000
Employer contributions	0		300,000,000
Benefits paid	(56,000,000)		(52,000,000)
Fair value of plan assets at December 31	2,035,000,000		1,955,000,000		1,508,000,000
Projected benefit obligation at January 1	1,897,000,000		1,592,000,000
Service cost	37,000,000		33,000,000		29,000,000
Interest cost	80,000,000		79,000,000		76,000,000
Actuarial (gain) loss	(260,000,000)		245,000,000
Transfer between plans	33,000,000		0
Projected benefit obligation at December 31	1,731,000,000		1,897,000,000		1,592,000,000
Accumulated benefit obligation	1,598,000,000		1,718,000,000
Funded Status at December 31	304,000,000	[1],[2]	58,000,000	[1],[2]
Weighted-average assumptions, discount rate, percent	5.17%		4.20%
Weighted-average assumptions, rate of compensation increase, percent	4.00%		4.00%
Accumulated other comprehensive income (loss), net actuarial loss	(403,000,000)		(743,000,000)
Accumulated Other Comprehensive Income (Loss), Net Prior Service Cost (Credit), before Tax	(31,000,000)		(5,000,000)
Balance at December 31	(434,000,000)		(748,000,000)
Defined Benefit Pension Plans | Non-Qualified Plan
Fair value of plan assets at January 1	0
Benefits paid	(9,000,000)		(9,000,000)
Fair value of plan assets at December 31	0		0
Projected benefit obligation at January 1	245,000,000		210,000,000
Service cost	4,000,000		4,000,000		3,000,000
Interest cost	9,000,000		10,000,000		11,000,000
Actuarial (gain) loss	(21,000,000)		30,000,000
Transfer between plans	(33,000,000)		0
Projected benefit obligation at December 31	195,000,000		245,000,000		210,000,000
Accumulated benefit obligation	163,000,000		209,000,000
Funded Status at December 31	(195,000,000)	[1],[2]	(245,000,000)	[1],[2]
Weighted-average assumptions, discount rate, percent	5.17%		4.20%
Weighted-average assumptions, rate of compensation increase, percent	4.00%		4.00%
Accumulated other comprehensive income (loss), net actuarial loss	(73,000,000)		(106,000,000)
Accumulated Other Comprehensive Income (Loss), Net Prior Service Cost (Credit), before Tax	28,000,000		2,000,000
Balance at December 31	(45,000,000)		(104,000,000)
Postretirement Benefit Plan
Fair value of plan assets at January 1	72,000,000		69,000,000
Actual return on plan assets	(2,000,000)		4,000,000		3,000,000
Employer contributions	3,000,000		4,000,000
Benefits paid	(6,000,000)		(5,000,000)
Fair value of plan assets at December 31	67,000,000		72,000,000		69,000,000
Projected benefit obligation at January 1	79,000,000		78,000,000
Service cost	0		0
Interest cost	3,000,000		3,000,000		4,000,000
Actuarial (gain) loss	(7,000,000)		3,000,000
Transfer between plans	0		0
Projected benefit obligation at December 31	69,000,000		79,000,000		78,000,000
Accumulated benefit obligation	69,000,000		79,000,000
Funded Status at December 31	(2,000,000)	[1],[2]	(7,000,000)	[1],[2]
Weighted-average assumptions, discount rate, percent	4.59%		3.81%
Healthcare cost trend rate assumed for next year	7.50%		8.00%
Rate to which the healthcare cost trend rate is assumed to decline (the ultimate trend rate), percent	5.00%		5.00%
Year when healthcare cost trend rate reaches the ultimate trend rate	2033		2033
Accumulated other comprehensive income (loss), net actuarial loss	(23,000,000)		(27,000,000)
Accumulated Other Comprehensive Income (Loss), Net Prior Service Cost (Credit), before Tax	(3,000,000)		(3,000,000)
Balance at December 31	$ (26,000,000)		$ (30,000,000)

[1] Based on projected benefit obligation for defined benefit pension plans and accumulated benefit obligation for postretirement benefit plan.

[2] The Corporation recognizes the overfunded and underfunded status of the plans in “accrued income and other assets” and “accrued expenses and other liabilities,” respectively, on the consolidated balance sheets.