Derivative Instruments (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended			3 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Mar. 31, 2011 December 31, 2012 Swap 1 and 2 [Member] Swap [Member]	Dec. 31, 2012 December 31, 2012 - Swap 1 [Member] Swap [Member]	Dec. 31, 2011 December 31, 2012 - Swap 1 [Member] Swap [Member]	Dec. 31, 2012 December 31, 2012 - Swap 2 [Member] Swap [Member]	Dec. 31, 2011 December 31, 2012 - Swap 2 [Member] Swap [Member]	Dec. 31, 2012 May 9, 2016 [Member] Swap [Member]	Dec. 31, 2011 May 9, 2016 [Member] Swap [Member]	Jul. 31, 2011 May 9, 2016 [Member] Swap [Member]
Derivative [Line Items]
Stated Interest Rate					3.105%	3.105%	3.105%	3.105%	2.02%	2.02%
Pre-tax (charge) on derivative instruments	$ 1,879	$ (4,881)	$ 0	$ (3,900)
Net (gain) loss on derivative instruments	(1,879)	4,881	0
Notional Amount					0	59,500	0	35,000	72,188	75,000	75,000
Market Value (Liability)					$ 0	$ (1,394)	$ 0	$ (820)	$ (3,146)	$ (2,810)