Summary of Significant Accounting Policies - Impact of Recently Issued Accounting Standards (Details) - Forecast - ASU 2016-02 Leases $ in Millions	Dec. 31, 2019 USD ($)
Minimum
Impact of Recently Issued Accounting Standards—Not Yet Adopted
Operating lease asset	$ 175
Operating lease liability	175
Maximum
Impact of Recently Issued Accounting Standards—Not Yet Adopted
Operating lease asset	195
Operating lease liability	$ 195