Derivative Instruments and Hedging Activities (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Fair Value of Derivative Instruments
Liability Derivatives, Current Notional	$ 1,137,767,000
Other Assets [Member] | Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Asset Derivatives, Current Notional	460,970,000	18,970,000
Asset Derivatives, Fair Value	5,434,000	903,000
Other Assets [Member] | Not Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Asset Derivatives, Current Notional	343,407,000	447,532,000
Asset Derivatives, Fair Value	673,000	155,000
Accounts Payable, Accrued Expenses and Other Liabilities [Member] | Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Liability Derivatives, Current Notional	1,098,780,000	1,301,144,000
Liability Derivatives, Fair Value	91,222,000	107,630,000
Accounts Payable, Accrued Expenses and Other Liabilities [Member] | Not Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Liability Derivatives, Current Notional	38,987,000	39,052,000
Liability Derivatives, Fair Value	15,467,000	15,477,000
Interest rate caps [Member] | Other Assets [Member] | Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Asset Derivatives, Current Notional	330,000,000
Asset Derivatives, Fair Value	208,000
Interest rate caps [Member] | Other Assets [Member] | Not Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Asset Derivatives, Current Notional	266,925,000	447,532,000
Asset Derivatives, Fair Value	50,000	155,000
Interest rate caps [Member] | Accounts Payable, Accrued Expenses and Other Liabilities [Member] | Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Liability Derivatives, Current Notional	0
Liability Derivatives, Fair Value	0
Interest rate caps [Member] | Accounts Payable, Accrued Expenses and Other Liabilities [Member] | Not Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Liability Derivatives, Current Notional	0	0
Liability Derivatives, Fair Value	0	0
Interest rate swaps [Member] | Other Assets [Member] | Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Asset Derivatives, Current Notional	0	0
Asset Derivatives, Fair Value	0	0
Interest rate swaps [Member] | Accounts Payable, Accrued Expenses and Other Liabilities [Member] | Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Liability Derivatives, Current Notional	870,995,000	961,359,000
Liability Derivatives, Fair Value	79,406,000	97,858,000
Total Return Swap [Member]
Fair Value of Derivative Instruments
Liability Derivatives, Current Notional	266,772,000
Total Return Swap [Member] | Other Assets [Member] | Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Asset Derivatives, Current Notional	130,970,000	18,970,000
Asset Derivatives, Fair Value	5,226,000	903,000
Total Return Swap [Member] | Other Assets [Member] | Not Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Asset Derivatives, Current Notional	76,482,000	0
Asset Derivatives, Fair Value	623,000	0
Total Return Swap [Member] | Accounts Payable, Accrued Expenses and Other Liabilities [Member] | Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Liability Derivatives, Current Notional	227,785,000	339,785,000
Liability Derivatives, Fair Value	11,816,000	9,772,000
Total Return Swap [Member] | Accounts Payable, Accrued Expenses and Other Liabilities [Member] | Not Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Liability Derivatives, Current Notional	38,987,000	39,052,000
Liability Derivatives, Fair Value	$ 15,467,000	$ 15,477,000