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Fair Value Measurements (Details 1) - USD ($) $ in Millions | Jun. 30, 2019 | Dec. 31, 2018
--- | --- | ---
Debt Instrument [Line Items] |  |
Notes payable, carrying value | $ 5,948.5 | $ 5,936.5
Debt instruments, fair value | 6,360.4 | 6,037.6
2.900% Senior Notes due 2020 |  |
Debt Instrument [Line Items] |  |
Notes payable, fair value | 1,507.5 | 1,489.5
Notes payable, carrying value | 1,491.1 | 1,480.8
3.625% Senior Notes due 2022 |  |
Debt Instrument [Line Items] |  |
Notes payable, fair value | 1,032.3 | 1,000.4
Notes payable, carrying value | 996.0 | 995.5
4.050% Senior Notes due 2025 |  |
Debt Instrument [Line Items] |  |
Notes payable, fair value | 1,867.4 | 1,745.1
Notes payable, carrying value | 1,738.7 | 1,737.8
5.200% Senior Notes due 2045 |  |
Debt Instrument [Line Items] |  |
Notes payable, fair value | 1,953.2 | 1,802.6
Notes payable, carrying value | $ 1,722.7 | $ 1,722.4

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