Recent Accounting Developments Recent Accounting Developments (Details) - Scenario, Forecast - Accounting Standards Update 2016-02 $ in Billions	Jan. 01, 2019 USD ($)
Minimum
Adjustments for New Accounting Pronouncements [Line Items]
Operating lease, right-of-use asset	$ 0.8
Operating lease, liability	0.8
Maximum
Adjustments for New Accounting Pronouncements [Line Items]
Operating lease, right-of-use asset	1.2
Operating lease, liability	$ 1.2