Fair Value of Derivatives and Financial Instruments (Textual) (Details)	3 Months Ended
	Mar. 31, 2019 USD ($) Contract $ / shares	Dec. 31, 2018 USD ($)
Derivative
Preferred Stock, Redemption Price Per Share | $ / shares	$ 50.00
Preferred Stock, Redemption Date	Oct. 01, 2026
Designated as Hedging Instrument | Interest Rate Swap
Derivative
Derivative, Number of Instruments Held | Contract	4
Derivative, Notional Amount	$ 300,000,000
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	1,600,000
Fixed Rate Debt
Derivative
Notes Payable Excluding Interest Rate Swaps and Cap Agreements	3,600,000,000	$ 3,100,000,000
Notes Payable, Fair Value Disclosure	3,700,000,000	3,100,000,000
Floating Rate Debt [Member]
Derivative
Notes Payable Excluding Interest Rate Swaps and Cap Agreements	1,000,000,000	1,100,000,000
Notes Payable, Fair Value Disclosure	$ 1,000,000,000	1,100,000,000
Minimum [Member] | Conventional Variable Rate Debt [Member]
Derivative
Debt Renewal Period	30 days
Maximum [Member] | Conventional Variable Rate Debt [Member]
Derivative
Debt Renewal Period	90 days
Fair Value, Measurements, Recurring [Member]
Derivative
Embedded Derivative, Fair Value of Embedded Derivative Asset	$ 18,100,000	18,600,000
Interest Rate Derivative Assets, at Fair Value	2,500,000	3,700,000
Interest Rate Derivative Liabilities, at Fair Value	0	$ 5,300,000
net liability position [Member]
Derivative
Credit Risk Related Contingent Features Termination Value	$ 0