Consolidated Statements of Comprehensive Income (Parenthetical) (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Consolidated Statements of Comprehensive Income [Abstract]
Change in fair value of interest rate swap agreements designated as cash flow hedges, tax	$ 24	$ 237	$ 62	$ 279
Unrealized gains arising during the period, net of tax		49	(7)	17
Reclassification adjustment for losses included in net income, tax				(139)
Unrealized gains arising during the period, tax	(611)	(3,441)	(2,419)	(7,998)
Reclassification adjustment for accumulated gains included in net income	$ 36	$ 29	$ 490	$ 55