Income Tax (Details 4) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Domestic Country [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 3,249
Expiration period for net operating loss carryforwards	2018
Domestic Country [Member] | Capital Loss Carryforwards [Member]
Capital Loss Carryforwards [Line Items]
Capital loss carryforwards	405
Expiration period for capital loss carryforwards	2014
Foreign Country [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	1,438
Expiration period for net operating loss carryforwards	2013
Foreign Country [Member] | Capital Loss Carryforwards [Member]
Capital Loss Carryforwards [Line Items]
Capital loss carryforwards	52
Expiration period for capital loss carryforwards	2014
State Country [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	453
Expiration period for net operating loss carryforwards	2013
State Country [Member] | Capital Loss Carryforwards [Member]
Capital Loss Carryforwards [Line Items]
Capital loss carryforwards	$ 0