Consolidated Statements Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Consolidated Statements Of Comprehensive Income [Abstract]
Net income	$ 188,044	$ 170,077	$ 146,255
Unrealized (loss) gain on derivatives qualifying as hedges
Unrealized (loss) gain on cash flow hedge, net of tax of $6, $(192) and $372 for 2011, 2010 and 2009, respectively	(10)	331	(645)
Less: reclassification adjustment for loss on cash flow hedge included in net income, net of tax of $(71), $(275) and $(1,329) for 2011, 2010 and 2009, respectively	121	471	2,312
Unrealized gain (loss) on available for sale securities
Unrealized gain (loss) on securities, net of tax of $(1), $12 and $2 for 2011, 2010 and 2009, respectively	3	(22)	(3)
Less: reclassification adjustment for loss (gain) on sale of securities included in net income, net of tax of $(1), $(8) and $3 for 2011, 2010 and 2009, respectively	2	14	(6)
Other comprehensive income	116	794	1,658
Comprehensive income	$ 188,160	$ 170,871	$ 147,913