Fair Value Measurements - Separate Account Assets (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Financial assets and financial liabilities carried at fair value [Line Items]
Guaranteed separate accounts	$ 548		$ 569
Non-guaranteed separate accounts	7,704	[1]	7,188	[2]
Total separate account assets	8,252		7,757
Separate Account Assets [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Balance at January 1,	1,005		750
Policyholder gains (losses)	82	[3]	55	[3]
Purchases, issuances, settlements:
Purchases	173		283
Sales	(14)		(6)
Settlements	(209)		(90)
Total purchases, sales, settlements	(50)		187
Transfers into/(out of) Level 3:
Transfers into Level 3	5		17
Transfers out of Level 3	(7)		(4)
Total transfers into/(out of) Level 3	(2)		13
Balance at December 31,	1,035		1,005
Policyholder Gains Losses Attributable To Instruments Still Held	76		49
Pension Benefits [Member]
Financial assets and financial liabilities carried at fair value [Line Items]
Non-guaranteed separate accounts	3,800		3,400
Fair Value Inputs Level 1 [Member]
Financial assets and financial liabilities carried at fair value [Line Items]
Guaranteed separate accounts	264		245
Non-guaranteed separate accounts	1,844		1,925
Total separate account assets	2,108		2,170
Fair Value Inputs Level 2 [Member]
Financial assets and financial liabilities carried at fair value [Line Items]
Guaranteed separate accounts	284		324
Non-guaranteed separate accounts	4,825		4,258
Total separate account assets	5,109		4,582
Fair Value Inputs Level 3 [Member]
Financial assets and financial liabilities carried at fair value [Line Items]
Guaranteed separate accounts	0		0
Non-guaranteed separate accounts	1,035		1,005
Total separate account assets	1,035		1,005
Fair Value Inputs Level 3 [Member] | Pension Benefits [Member]
Financial assets and financial liabilities carried at fair value [Line Items]
Non-guaranteed separate accounts	$ 983		$ 956

[1] As of December 31, 2013, non-guaranteed separate accounts included $3.8 billion in assets supporting the Company's pension plans, including $983 million classified in Level 3.

[2] As of December 31, 2012, non-guaranteed separate accounts included $3.4 billion in assets supporting the Company's pension plans, including $956 million classified in Level 3.

[3] Included in this amount were gains of $76 million attributable to instruments still held at December 31, 2013 and gains of $49 million attributable to instruments still held at December 31, 2012.