Fair Value Measurements (Details 1) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument
Notes payable, fair value	$ 6,553.6	$ 6,037.6
2.90% Senior Notes due 2020
Debt Instrument
Notes payable, fair value	1,509.6	1,489.5
3.625% Senior Notes due 2022
Debt Instrument
Notes payable, fair value	1,038.9	1,000.4
4.05% Senior Notes due 2025
Debt Instrument
Notes payable, fair value	1,897.2	1,745.1
5.20% Senior Notes due 2045
Debt Instrument
Notes payable, fair value	$ 2,107.9	$ 1,802.6