Fair Value of Financial Instruments (Schedule of Interest Rate Swaps) (Details) (Interest Rate Swap [Member], USD $)	12 Months Ended
	Dec. 31, 2014
Interest Rate Swaps One [Member]
Derivative [Line Items]
Notional Amount, Liability	$ 300,000,000
Fixed Interest Rate	3.447%
Termination Date	Aug. 08, 2016
Fair Value of Liability	13,000,000
Interest Rate Swaps Two [Member]
Derivative [Line Items]
Notional Amount, Liability	200,000,000
Fixed Interest Rate	3.429%
Termination Date	Aug. 19, 2016
Fair Value of Liability	9,000,000
Interest Rate Swaps Three [Member]
Derivative [Line Items]
Notional Amount, Liability	100,000,000
Fixed Interest Rate	3.401%
Termination Date	Aug. 19, 2016
Fair Value of Liability	4,000,000
Interest Rate Swaps Four [Member]
Derivative [Line Items]
Notional Amount, Liability	200,000,000
Fixed Interest Rate	3.50%
Termination Date	Aug. 30, 2016
Fair Value of Liability	9,000,000
Interest Rate Swaps Five [Member]
Derivative [Line Items]
Notional Amount, Liability	100,000,000
Fixed Interest Rate	3.005%
Termination Date	Nov. 30, 2016
Fair Value of Liability	4,000,000
Interest Rate Swaps Six [Member]
Derivative [Line Items]
Notional Amount, Liability	200,000,000
Fixed Interest Rate	2.055%
Termination Date	Jul. 25, 2019
Fair Value of Liability	4,000,000
Interest Rate Swaps Seven [Member]
Derivative [Line Items]
Notional Amount, Liability	200,000,000
Fixed Interest Rate	2.059%
Termination Date	Jul. 25, 2019
Fair Value of Liability	4,000,000
Interest Rate Swaps Eight [Member]
Derivative [Line Items]
Notional Amount, Liability	200,000,000
Fixed Interest Rate	2.613%
Termination Date	Aug. 30, 2019
Fair Value of Liability	4,000,000	[1]
Interest Rate Swaps Nine [Member]
Derivative [Line Items]
Notional Amount, Liability	200,000,000
Fixed Interest Rate	2.515%
Termination Date	Aug. 30, 2019
Fair Value of Liability	3,000,000	[2]
Interest Rate Swaps Ten [Member]
Derivative [Line Items]
Notional Amount, Liability	300,000,000
Fixed Interest Rate	2.892%
Termination Date	Aug. 30, 2020
Fair Value of Liability	8,000,000	[1]
Interest Rate Swaps Eleven [Member]
Derivative [Line Items]
Notional Amount, Liability	300,000,000
Fixed Interest Rate	2.738%
Termination Date	Aug. 30, 2020
Fair Value of Liability	$ 6,000,000	[2]

[1] This interest rate swap becomes effective August 30, 2015.

[2] This interest rate swap becomes effective August 28, 2015.