Basis of Presentation -Narrative (Details) - Estimated Impact of Lease Accounting Standard $ in Millions	Sep. 30, 2018 USD ($)
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in assets	$ 800
Increase in liabilities	800
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in assets	1,200
Increase in liabilities	$ 1,200