Recently Issued Accounting Standards (Details Textual) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019	Jan. 01, 2018	Jan. 01, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease liability	$ 243								$ 243
Deferred Tax Asset, Lease Liability Recognized												$ 68
Right of use asset	241								241			267
Cumulative effect of change in accounting principle													$ (3)	$ (7)
Operating Income (Loss)	$ 195	$ 11	$ 171	$ 109	$ 194	$ 176	$ 171	$ 113	$ 486	$ 654	$ 552
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease liability												$ 265
Accounting Standards Update 2017-12
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle					2					2
Adjustments for New Accounting Pronouncement
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Income (Loss)											$ 4
Accumulated Other Comprehensive Income (Loss)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle					(17)					(17)			(17)
Accumulated Other Comprehensive Income (Loss) | Accounting Standards Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle					17					17
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle													$ 14	$ (7)
Retained Earnings | Accounting Standards Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle					$ 17					$ 17