Derivative Financial Instruments (Details 3) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Gross amounts not offset in consolidated balance sheets
Cash collateral received pledged, total derivative liabilities	$ 0	$ 0
Derivatives not designated as cash flow hedges
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative assets	0	1,000,000
Derivative liability	(4,000,000)	(12,000,000)
Gross and net amounts presented in consolidated balance sheets, net assets	(4,000,000)	(11,000,000)
Gross amounts not offset in consolidated balance sheets
Financial instruments, total derivative assets	0	1,000,000
Financial instruments, total derivative liabilities	0	(1,000,000)
Financial instruments, net derivative (asset) liability	0	0
Cash collateral received pledged, total derivative assets	0	0
Cash collateral received pledged, total derivative liabilities	0	0
Cash collateral received pledged, net derivative asset liabilities	0	0
Net amount, total derivative assets	0	0
Net amount, total derivative liabilities	(4,000,000)	(11,000,000)
Net amount, net derivative asset (liability)	$ (4,000,000)	$ (11,000,000)