Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Net income	$ 120,687	$ 110,396	$ 107,441
Other comprehensive income (loss), net of tax
Settlement of forward starting interest rate swap agreement	0	0	(8,663)
Amortization of loss on cash flow hedge	862	862	332
Foreign currency translation adjustment, net	237	615	1,265
Actuarial loss (net of income tax of $48 for the year ended December 31, 2012)	80	0	0
Settlement of pension plan (net of income tax of $840 for the year ended December 31, 2012)	1,406	0	0
Actuarial pension loss (net of income tax of $649 and $275 for the years ended December 31, 2011 and 2010, respectively)	0	(1,086)	(459)
Other comprehensive income (loss), net of tax	2,585	391	(7,525)
Comprehensive income	$ 123,272	$ 110,787	$ 99,916