Debt Interest Rate Swaps 2 (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Forward-starting Interest Rate Swap 1 [Member]
Derivative [Line Items]
Forward-starting interest rate swap agreement, inception date	May 08, 2014
Forward-starting interest rate swap agreement, effective date	Oct. 19, 2016
Forward-starting interest rate swap agreement, notional amount	$ 25.0
Forward-starting interest rate swap agreement, fixed interest rate	2.52%
Forward-starting interest rate swap agreement, termination date	Sep. 20, 2018
Forward-starting Interest Rate Swap 2 [Member]
Derivative [Line Items]
Forward-starting interest rate swap agreement, inception date	May 14, 2014
Forward-starting interest rate swap agreement, effective date	Oct. 19, 2016
Forward-starting interest rate swap agreement, notional amount	50.0
Forward-starting interest rate swap agreement, fixed interest rate	2.45%
Forward-starting interest rate swap agreement, termination date	Sep. 20, 2018
Forward-starting Interest Rate Swap 3 [Member]
Derivative [Line Items]
Forward-starting interest rate swap agreement, inception date	May 19, 2014
Forward-starting interest rate swap agreement, effective date	Oct. 19, 2016
Forward-starting interest rate swap agreement, notional amount	50.0
Forward-starting interest rate swap agreement, fixed interest rate	2.339%
Forward-starting interest rate swap agreement, termination date	Sep. 20, 2018
Forward-starting Interest Rate Swap 4 [Member]
Derivative [Line Items]
Forward-starting interest rate swap agreement, inception date	May 28, 2014
Forward-starting interest rate swap agreement, effective date	Oct. 19, 2016
Forward-starting interest rate swap agreement, notional amount	$ 25.0
Forward-starting interest rate swap agreement, fixed interest rate	2.256%
Forward-starting interest rate swap agreement, termination date	Sep. 20, 2018