Leases - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Jan. 01, 2019
Lessee, Lease, Description [Line Items]
Operating lease assets	$ 117
Operating lease liability	125
Lease income	$ 81	$ 85
Accounting Standards Update 2016-02
Lessee, Lease, Description [Line Items]
Operating lease assets			$ 126
Operating lease liability			$ 133