Leases - Lease activity (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Leases [Abstract]
Operating leases	$ 11
Short-term leases	0
Total lease expense	11
Cash paid for amounts included in the measurement of lease liabilities reported in operating cash flows	12
Right-of-use assets obtained in exchange for new lease liabilities	$ 3
Weighted-average remaining lease term (in years)	5 years 10 months 24 days
Weighted-average discount rate (percent)	4.10%