Fair Value Measurements and Interest Rate Swaps (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Derivative [Line Items]
Interest rate swap agreements, termination date	Oct. 19, 2016
Interest Rate Swap 1 [Member]
Derivative [Line Items]
Interest rate swap agreement, effective date	Nov. 21, 2011
Interest rate swap agreement, notional amount	25.0
Interest rate swap agreement, fixed interest rate	1.185%
Interest Rate Swap 2 [Member]
Derivative [Line Items]
Interest rate swap agreement, effective date	Nov. 21, 2011
Interest rate swap agreement, notional amount	25.0
Interest rate swap agreement, fixed interest rate	1.185%
Interest Rate Swap 3 [Member]
Derivative [Line Items]
Interest rate swap agreement, effective date	Dec. 21, 2011
Interest rate swap agreement, notional amount	50.0
Interest rate swap agreement, fixed interest rate	1.10%
Interest Rate Swap 4 [Member]
Derivative [Line Items]
Interest rate swap agreement, effective date	Jan. 17, 2012
Interest rate swap agreement, notional amount	25.0
Interest rate swap agreement, fixed interest rate	1.05%
Interest Rate Swap 5 [Member]
Derivative [Line Items]
Interest rate swap agreement, effective date	Jan. 19, 2012
Interest rate swap agreement, notional amount	25.0
Interest rate swap agreement, fixed interest rate	0.99%