Reportable Business Segments (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Reconciliation of segment operating income to consolidated income before income taxes
Segment operating income	$ 185,279	$ 186,085
Interest expense	(13,749)	(10,016)
Stock-based compensation expense	(7,491)	(6,320)
Income before income taxes	173,717	177,773
Total
Reconciliation of segment operating income to consolidated income before income taxes
Segment operating income	201,535	201,571
Unallocated amount to segment
Reconciliation of segment operating income to consolidated income before income taxes
Interest expense	(13,749)	(10,016)
Interest Income	2,540	1,818
Stock-based compensation expense	(7,491)	(6,320)
Other costs, net	$ (9,118)	$ (9,280)