Fair Value of Financial Instruments (Schedule of Interest Rate Swaps) (Details) (Interest Rate Swap [Member], USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
Interest Rate Swaps One [Member]
Derivative [Line Items]
Notional Amount	$ 100,000
Fixed Interest Rate	3.352%
Termination Date	Oct. 23, 2012
Fair Value of Liability	186
Interest Rate Swaps Two [Member]
Derivative [Line Items]
Notional Amount	125,000
Fixed Interest Rate	4.375%
Termination Date	Nov. 23, 2012
Fair Value of Liability	729
Interest Rate Swaps Three [Member]
Derivative [Line Items]
Notional Amount	75,000
Fixed Interest Rate	4.38%
Termination Date	Nov. 23, 2012
Fair Value of Liability	436
Interest Rate Swaps Four [Member]
Derivative [Line Items]
Notional Amount	150,000
Fixed Interest Rate	5.02%
Termination Date	Nov. 30, 2012
Fair Value of Liability	1,146
Interest Rate Swaps Five [Member]
Derivative [Line Items]
Notional Amount	200,000
Fixed Interest Rate	2.242%
Termination Date	Feb. 28, 2013
Fair Value of Liability	1,558
Interest Rate Swaps Six [Member]
Derivative [Line Items]
Notional Amount	100,000
Fixed Interest Rate	5.023%
Termination Date	May 30, 2013
Fair Value of Liability	3,114
Interest Rate Swaps Seven [Member]
Derivative [Line Items]
Notional Amount	300,000
Fixed Interest Rate	5.242%
Termination Date	Aug. 06, 2013
Fair Value of Liability	12,533
Interest Rate Swaps Eight [Member]
Derivative [Line Items]
Notional Amount	100,000
Fixed Interest Rate	5.038%
Termination Date	Aug. 30, 2013
Fair Value of Liability	4,313
Interest Rate Swaps Nine [Member]
Derivative [Line Items]
Notional Amount	50,000
Fixed Interest Rate	3.586%
Termination Date	Oct. 23, 2013
Fair Value of Liability	1,729
Interest Rate Swaps Ten [Member]
Derivative [Line Items]
Notional Amount	50,000
Fixed Interest Rate	3.524%
Termination Date	Oct. 23, 2013
Fair Value of Liability	1,696
Interest Rate Swaps Eleven [Member]
Derivative [Line Items]
Notional Amount	100,000
Fixed Interest Rate	5.05%
Termination Date	Nov. 30, 2013
Fair Value of Liability	5,495
Interest Rate Swaps Twelve [Member]
Derivative [Line Items]
Notional Amount	200,000
Fixed Interest Rate	2.07%
Termination Date	Dec. 19, 2013
Fair Value of Liability	4,217
Interest Rate Swaps Thirteen [Member]
Derivative [Line Items]
Notional Amount	100,000
Fixed Interest Rate	5.231%
Termination Date	Jul. 25, 2014
Fair Value of Liability	8,824
Interest Rate Swaps Fourteen [Member]
Derivative [Line Items]
Notional Amount	100,000
Fixed Interest Rate	5.231%
Termination Date	Jul. 25, 2014
Fair Value of Liability	8,823
Interest Rate Swaps Fifteen [Member]
Derivative [Line Items]
Notional Amount	200,000
Fixed Interest Rate	5.16%
Termination Date	Jul. 25, 2014
Fair Value of Liability	17,390
Interest Rate Swaps Sixteen [Member]
Derivative [Line Items]
Notional Amount	75,000
Fixed Interest Rate	5.041%
Termination Date	Jul. 25, 2014
Fair Value of Liability	6,359
Interest Rate Swaps Seventeen [Member]
Derivative [Line Items]
Notional Amount	125,000
Fixed Interest Rate	5.022%
Termination Date	Jul. 25, 2014
Fair Value of Liability	10,555
Interest Rate Swaps Eighteen [Member]
Derivative [Line Items]
Notional Amount	100,000
Fixed Interest Rate	2.621%
Termination Date	Jul. 25, 2014
Fair Value of Liability	4,095
Interest Rate Swaps Nineteen [Member]
Derivative [Line Items]
Notional Amount	100,000
Fixed Interest Rate	3.11%
Termination Date	Jul. 25, 2014
Fair Value of Liability	4,981
Interest Rate Swaps Twenty [Member]
Derivative [Line Items]
Notional Amount	100,000
Fixed Interest Rate	3.258%
Termination Date	Jul. 25, 2014
Fair Value of Liability	5,249
Interest Rate Swaps Twenty One [Member]
Derivative [Line Items]
Notional Amount	200,000
Fixed Interest Rate	2.693%
Termination Date	Oct. 26, 2014
Fair Value of Liability	9,575
Interest Rate Swaps Twenty Two [Member]
Derivative [Line Items]
Notional Amount	300,000
Fixed Interest Rate	3.447%
Termination Date	Aug. 08, 2016
Fair Value of Liability	32,294
Interest Rate Swaps Twenty Three [Member]
Derivative [Line Items]
Notional Amount	200,000
Fixed Interest Rate	3.429%
Termination Date	Aug. 19, 2016
Fair Value of Liability	21,510
Interest Rate Swaps Twenty Four [Member]
Derivative [Line Items]
Notional Amount	100,000
Fixed Interest Rate	3.401%
Termination Date	Aug. 19, 2016
Fair Value of Liability	10,654
Interest Rate Swaps Twenty Five [Member]
Derivative [Line Items]
Notional Amount	200,000
Fixed Interest Rate	3.50%
Termination Date	Aug. 30, 2016
Fair Value of Liability	22,165
Interest Rate Swaps Twenty Six [Member]
Derivative [Line Items]
Notional Amount	100,000
Fixed Interest Rate	3.005%
Termination Date	Nov. 30, 2016
Fair Value of Liability	$ 9,584