Derivative Instruments and Hedging Activities (Details) - USD ($)	Sep. 30, 2015	Dec. 31, 2014
Fair Value of Derivative Instruments
Liability Derivatives, Current Notional	$ 1,095,638,000
Other Assets [Member] | Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Asset Derivatives, Current Notional	479,200,000	$ 479,200,000
Asset Derivatives, Fair Value	7,977,000	6,493,000
Other Assets [Member] | Not Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Asset Derivatives, Current Notional	417,586,000	306,932,000
Asset Derivatives, Fair Value	5,435,000	1,869,000
Accounts Payable, Accrued Expenses and Accrued Liabilities [Member] | Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Liability Derivatives, Current Notional	1,057,282,000	1,086,939,000
Liability Derivatives, Fair Value	71,378,000	87,264,000
Accounts Payable, Accrued Expenses and Accrued Liabilities [Member] | Not Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Liability Derivatives, Current Notional	38,356,000	38,425,000
Liability Derivatives, Fair Value	14,200,000	15,098,000
Interest rate caps [Member] | Other Assets [Member] | Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Asset Derivatives, Current Notional	330,000,000	330,000,000
Asset Derivatives, Fair Value	0	114,000
Interest rate caps [Member] | Other Assets [Member] | Not Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Asset Derivatives, Current Notional	316,396,000	205,522,000
Asset Derivatives, Fair Value	0	12,000
Interest rate caps [Member] | Accounts Payable, Accrued Expenses and Accrued Liabilities [Member] | Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Liability Derivatives, Current Notional	0	0
Liability Derivatives, Fair Value	0	0
Interest rate caps [Member] | Accounts Payable, Accrued Expenses and Accrued 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 Accrued Liabilities [Member] | Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Liability Derivatives, Current Notional	734,497,000	869,154,000
Liability Derivatives, Fair Value	61,096,000	75,281,000
TROR [Member]
Fair Value of Derivative Instruments
Liability Derivatives, Current Notional	361,141,000
TROR [Member] | Other Assets [Member] | Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Asset Derivatives, Current Notional	149,200,000	149,200,000
Asset Derivatives, Fair Value	7,977,000	6,379,000
TROR [Member] | Other Assets [Member] | Not Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Asset Derivatives, Current Notional	101,190,000	101,410,000
Asset Derivatives, Fair Value	5,435,000	1,857,000
TROR [Member] | Accounts Payable, Accrued Expenses and Accrued Liabilities [Member] | Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Liability Derivatives, Current Notional	322,785,000	217,785,000
Liability Derivatives, Fair Value	10,282,000	11,983,000
TROR [Member] | Accounts Payable, Accrued Expenses and Accrued Liabilities [Member] | Not Designated as Hedging Instrument [Member]
Fair Value of Derivative Instruments
Liability Derivatives, Current Notional	38,356,000	38,425,000
Liability Derivatives, Fair Value	$ 14,200,000	$ 15,098,000