Debt and Lines of Credit - Schedule of Long-term Debt Outstanding (Parenthetical) (Details)	Mar. 31, 2019	Dec. 31, 2018
Notes due 2019 at 1.65%
Debt Instrument [Line Items]
Long-term debt stated interest rate (in percentage)	1.65%	1.65%
Notes due 2020 at 1.75%
Debt Instrument [Line Items]
Long-term debt stated interest rate (in percentage)	1.75%	1.75%
Notes due 2021 at 2.75%
Debt Instrument [Line Items]
Long-term debt stated interest rate (in percentage)	2.75%	2.75%
Notes due 2022 at 1.85%
Debt Instrument [Line Items]
Long-term debt stated interest rate (in percentage)	1.85%	1.85%
Notes due 2023 at 2.25%
Debt Instrument [Line Items]
Long-term debt stated interest rate (in percentage)	2.25%	2.25%
Notes due 2039 at 3.875%
Debt Instrument [Line Items]
Long-term debt stated interest rate (in percentage)	3.875%	3.875%
Notes due 2024 at 2.625%
Debt Instrument [Line Items]
Long-term debt stated interest rate (in percentage)	2.625%	2.625%
Notes due 2027 at 2.90%
Debt Instrument [Line Items]
Long-term debt stated interest rate (in percentage)	2.90%	2.90%
Notes due 2048 at 4.15%
Debt Instrument [Line Items]
Long-term debt stated interest rate (in percentage)	4.15%	4.15%