Derivative Instruments and Hedging Activities (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Fair Value of Derivative Instruments
Liability Derivative, Current Notional	$ 1,125,364,000
Other Assets [Member] | Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Asset Derivative, Current Notional	479,200,000	18,970,000
Asset Derivative, Fair Value	6,493,000	903,000
Other Assets [Member] | Not Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Asset Derivative, Current Notional	306,932,000	447,532,000
Asset Derivative, Fair Value	1,869,000	155,000
Accounts Payable, Accrued Expenses and Other Liabilities [Member] | Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Liability Derivative, Current Notional	1,086,939,000	1,301,144,000
Liability Derivative, Fair Value	87,264,000	107,630,000
Accounts Payable, Accrued Expenses and Other Liabilities [Member] | Not Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Liability Derivative, Current Notional	38,425,000	39,052,000
Liability Derivative, Fair Value	15,098,000	15,477,000
Interest rate caps [Member] | Other Assets [Member] | Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Asset Derivative, Current Notional	330,000,000
Asset Derivative, Fair Value	114,000
Interest rate caps [Member] | Other Assets [Member] | Not Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Asset Derivative, Current Notional	205,522,000	447,532,000
Asset Derivative, Fair Value	12,000	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 Derivative, Current Notional	0
Liability Derivative, 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 Derivative, Current Notional	0	0
Liability Derivative, Fair Value	0	0
Interest rate swaps [Member] | Other Assets [Member] | Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Asset Derivative, Current Notional	0	0
Asset Derivative, 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 Derivative, Current Notional	869,154,000	961,359,000
Liability Derivative, Fair Value	75,281,000	97,858,000
TROR [Member]
Fair Value of Derivative Instruments
Liability Derivative, Current Notional	256,210,000
TROR [Member] | Other Assets [Member] | Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Asset Derivative, Current Notional	149,200,000	18,970,000
Asset Derivative, Fair Value	6,379,000	903,000
TROR [Member] | Other Assets [Member] | Not Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Asset Derivative, Current Notional	101,410,000	0
Asset Derivative, Fair Value	1,857,000	0
TROR [Member] | Accounts Payable, Accrued Expenses and Other Liabilities [Member] | Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Liability Derivative, Current Notional	217,785,000	339,785,000
Liability Derivative, Fair Value	11,983,000	9,772,000
TROR [Member] | Accounts Payable, Accrued Expenses and Other Liabilities [Member] | Not Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Liability Derivative, Current Notional	38,425,000	39,052,000
Liability Derivative, Fair Value	$ 15,098,000	$ 15,477,000