Fair Value of Financial Instruments (Schedule of Interest Rate Swaps) (Details) (Interest Rate Swap [Member], USD $)	9 Months Ended
	Sep. 30, 2013
Derivative [Line Items]
Notional Amount	$ 2,400,000,000
Interest Rate Swaps One [Member]
Derivative [Line Items]
Notional Amount	50,000,000
Fixed Interest Rate	3.586%
Termination Date	Oct. 23, 2013
Fair Value of Liability	103,000
Interest Rate Swaps Two [Member]
Derivative [Line Items]
Notional Amount	50,000,000
Fixed Interest Rate	3.524%
Termination Date	Oct. 23, 2013
Fair Value of Liability	101,000
Interest Rate Swaps Three [Member]
Derivative [Line Items]
Notional Amount	100,000,000
Fixed Interest Rate	5.05%
Termination Date	Nov. 30, 2013
Fair Value of Liability	783,000
Interest Rate Swaps Four [Member]
Derivative [Line Items]
Notional Amount	200,000,000
Fixed Interest Rate	2.07%
Termination Date	Dec. 19, 2013
Fair Value of Liability	791,000
Interest Rate Swaps Five [Member]
Derivative [Line Items]
Notional Amount	100,000,000
Fixed Interest Rate	5.231%
Termination Date	Jul. 25, 2014
Fair Value of Liability	4,050,000
Interest Rate Swaps Six [Member]
Derivative [Line Items]
Notional Amount	100,000,000
Fixed Interest Rate	5.231%
Termination Date	Jul. 25, 2014
Fair Value of Liability	4,050,000
Interest Rate Swaps Seven [Member]
Derivative [Line Items]
Notional Amount	200,000,000
Fixed Interest Rate	5.16%
Termination Date	Jul. 25, 2014
Fair Value of Liability	7,983,000
Interest Rate Swaps Eight [Member]
Derivative [Line Items]
Notional Amount	75,000,000
Fixed Interest Rate	5.041%
Termination Date	Jul. 25, 2014
Fair Value of Liability	2,920,000
Interest Rate Swaps Nine [Member]
Derivative [Line Items]
Notional Amount	125,000,000
Fixed Interest Rate	5.022%
Termination Date	Jul. 25, 2014
Fair Value of Liability	4,847,000
Interest Rate Swaps Ten [Member]
Derivative [Line Items]
Notional Amount	100,000,000
Fixed Interest Rate	2.621%
Termination Date	Jul. 25, 2014
Fair Value of Liability	1,906,000
Interest Rate Swaps Eleven [Member]
Derivative [Line Items]
Notional Amount	100,000,000
Fixed Interest Rate	3.11%
Termination Date	Jul. 25, 2014
Fair Value of Liability	2,307,000
Interest Rate Swaps Twelve [Member]
Derivative [Line Items]
Notional Amount	100,000,000
Fixed Interest Rate	3.258%
Termination Date	Jul. 25, 2014
Fair Value of Liability	2,429,000
Interest Rate Swaps Thirteen [Member]
Derivative [Line Items]
Notional Amount	200,000,000
Fixed Interest Rate	2.693%
Termination Date	Oct. 26, 2014
Fair Value of Liability	5,120,000
Interest Rate Swaps Fourteen [Member]
Derivative [Line Items]
Notional Amount	300,000,000
Fixed Interest Rate	3.447%
Termination Date	Aug. 08, 2016
Fair Value of Liability	23,323,000
Interest Rate Swaps Fifteen [Member]
Derivative [Line Items]
Notional Amount	200,000,000
Fixed Interest Rate	3.429%
Termination Date	Aug. 19, 2016
Fair Value of Liability	15,543,000
Interest Rate Swaps Sixteen [Member]
Derivative [Line Items]
Notional Amount	100,000,000
Fixed Interest Rate	3.401%
Termination Date	Aug. 19, 2016
Fair Value of Liability	7,695,000
Interest Rate Swaps Seventeen [Member]
Derivative [Line Items]
Notional Amount	200,000,000
Fixed Interest Rate	3.50%
Termination Date	Aug. 30, 2016
Fair Value of Liability	16,055,000
Interest Rate Swaps Eighteen [Member]
Derivative [Line Items]
Notional Amount	100,000,000
Fixed Interest Rate	3.005%
Termination Date	Nov. 30, 2016
Fair Value of Liability	$ 6,855,000