Employee Benefit Plans (Pension plan and other postretirement plan assets that are measured at fair value and included in the Level 3 fair value category) (Details) (Level 3, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Benefits
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	$ 1,190	$ 1,285	$ 1,278
Actual return on plan assets:
Relating to assets still held at the reporting date	166	105	128
Relating to assets sold during the period	(122)	(62)	(67)
Purchases	153	129	215
Sales	(263)	(267)	(269)
Fair value of plan assets at end of year	1,124	1,190	1,285
Pension Benefits | Real estate:
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	321	304	271
Actual return on plan assets:
Relating to assets still held at the reporting date	15	21	38
Relating to assets sold during the period	(36)	(8)	(8)
Purchases	6	35	57
Sales	(79)	(31)	(54)
Fair value of plan assets at end of year	227	321	304
Pension Benefits | Private equity
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	456	448	400
Actual return on plan assets:
Relating to assets still held at the reporting date	98	46	70
Relating to assets sold during the period	(48)	(41)	(34)
Purchases	115	79	76
Sales	(91)	(76)	(64)
Fair value of plan assets at end of year	530	456	448
Pension Benefits | Debt
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	192	243	262
Actual return on plan assets:
Relating to assets still held at the reporting date	32	17	10
Relating to assets sold during the period	(34)	(11)	(10)
Purchases	32	15	34
Sales	(42)	(72)	(53)
Fair value of plan assets at end of year	180	192	243
Pension Benefits | Hedge funds
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	221	290	345
Actual return on plan assets:
Relating to assets still held at the reporting date	21	21	10
Relating to assets sold during the period	(4)	(2)	(15)
Purchases	0	0	48
Sales	(51)	(88)	(98)
Fair value of plan assets at end of year	187	221	290
Other Postretirement Plans
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	124	137	140
Actual return on plan assets:
Relating to assets still held at the reporting date	8	9	15
Relating to assets sold during the period	5	(1)	(6)
Purchases	10	9	16
Sales	(31)	(30)	(28)
Fair value of plan assets at end of year	116	124	137
Other Postretirement Plans | Real estate:
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	24	24	22
Actual return on plan assets:
Relating to assets still held at the reporting date	(2)	1	3
Relating to assets sold during the period	1	0	0
Purchases	1	2	3
Sales	(5)	(3)	(4)
Fair value of plan assets at end of year	19	24	24
Other Postretirement Plans | Private equity
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	58	63	61
Actual return on plan assets:
Relating to assets still held at the reporting date	6	3	11
Relating to assets sold during the period	3	(1)	(4)
Purchases	7	6	8
Sales	(14)	(13)	(13)
Fair value of plan assets at end of year	60	58	63
Other Postretirement Plans | Debt
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	31	36	40
Actual return on plan assets:
Relating to assets still held at the reporting date	3	4	1
Relating to assets sold during the period	0	0	(1)
Purchases	2	1	3
Sales	(9)	(10)	(7)
Fair value of plan assets at end of year	27	31	36
Other Postretirement Plans | Hedge funds
Changes in fair value of plan assets:
Fair value of plan assets at beginning of year	11	14	17
Actual return on plan assets:
Relating to assets still held at the reporting date	1	1	0
Relating to assets sold during the period	1	0	(1)
Purchases	0	0	2
Sales	(3)	(4)	(4)
Fair value of plan assets at end of year	$ 10	$ 11	$ 14