Income Taxes - Net Operating Loss Carryforward Table (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Foreign [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward	$ 1,184
Foreign [Member] | Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, expiration date	Dec. 31, 2018
State [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward	$ 4,452
State [Member] | Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, expiration date	Dec. 31, 2018
State [Member] | Latest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards, expiration date	Dec. 31, 2037