Fair Value of Derivatives and Financial Instruments (Textual) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Derivative
Preferred Stock, Redemption Price Per Share	$ 50.00
Preferred Stock, Redemption Date	Oct. 01, 2026
Net liability position
Derivative
Credit risk related contingent features termination value	$ 1,200
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	1,900
Parent Company [Member]
Derivative
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	233	$ 0
Fixed Rate Debt
Derivative
Notes Payable Excluding Interest Rate Swaps and Cap Agreements	3,100,000		$ 3,200,000
Notes Payable, Fair Value Disclosure	3,200,000		3,300,000
Floating Rate Debt [Member]
Derivative
Notes Payable Excluding Interest Rate Swaps and Cap Agreements	1,400,000		1,300,000
Notes Payable, Fair Value Disclosure	$ 1,400,000		1,300,000
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	$ 18,500		21,200
Interest Rate Derivative Assets, at Fair Value	5,100		3,600
Interest Rate Derivative Liabilities, at Fair Value	$ 1,600		$ 1,300