Borrowings (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Schedule of Held-to-maturity Securities [Line Items]
Proceeds from Issuance of Debt	$ 992
3.2% Notes due 2023 [Member]
Schedule of Held-to-maturity Securities [Line Items]
Long-term Debt	$ 300
Stated interest rate	3.20%
3.75% Notes due 2028 [Member]
Schedule of Held-to-maturity Securities [Line Items]
Long-term Debt	$ 700
Stated interest rate	3.80%