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Financial Instruments and Derivatives - Additional Information (Details) | 9 Months Ended |
--- | --- | ---
Sep. 30, 2019 USD ($) Contract $ / shares | Dec. 31, 2018 USD ($)
Derivative |  |
Preferred Stock, Redemption Price Per Share | $ / shares | $ 50 |
Preferred Stock, Redemption Date | Oct. 01, 2026 |
net liability position [Member] |  |
Derivative |  |
Credit Risk Related Contingent Features Termination Value | $ 10,200,000 |
Fair Value, Measurements, Recurring [Member] |  |
Derivative |  |
Interest Rate Derivative Assets, at Fair Value | 500,000 | $ 3,700,000
Interest Rate Derivative Liabilities, at Fair Value | 10,500,000 | 5,300,000
Embedded Derivative, Fair Value of Embedded Derivative Asset | 38,200,000 | 18,600,000
Forward Swaps on future expected debt issuance [Member] |  |
Derivative |  |
Cash Flow Hedges Derivative Instruments at Fair Value, Net | $ 150,000,000.0 |
Maximum Length of Time Hedged in Cash Flow Hedge | 10 years |
Designated as Hedging Instrument | Interest Expense |  |
Derivative |  |
Change in fair value of interest rate derivatives included in AOCI and expected to be reclassified in the next 12 months | $ 1,000,000.0 |
Designated as Hedging Instrument | Interest Rate Swap [Member] |  |
Derivative |  |
Derivative, Number of Instruments Held | Contract | 4 |
Derivative, Notional Amount | $ 300,000,000.0 |
Conventional Variable Rate Debt [Member] | Minimum [Member] |  |
Derivative |  |
Debt Renewal Period | 30 days |
Conventional Variable Rate Debt [Member] | Maximum [Member] |  |
Derivative |  |
Debt Renewal Period | 90 days |
Fixed Rate Debt [Member] |  |
Derivative |  |
Notes Payable Excluding Interest Rate Swaps and Cap Agreements | $ 3,800,000,000 | 3,100,000,000
Notes Payable, Fair Value Disclosure | 4,100,000,000 | 3,100,000,000
Floating Rate Debt [Member] |  |
Derivative |  |
Notes Payable Excluding Interest Rate Swaps and Cap Agreements | 500,000,000 | 1,100,000,000
Notes Payable, Fair Value Disclosure | $ 500,000,000 | $ 1,100,000,000

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