Nature of Business and Significant Accounting Policies (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2010		Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010		Dec. 31, 2009
Numerator for earnings per share:
Earnings from continuing operations	$ 76,835	$ 64,390	[1]	$ 29,822	[1],[2]	$ 51,605	[1]	$ 70,070	[1]	$ 62,955	$ 59,454	$ 55,895	$ 222,652	$ 248,374	[3]	$ 230,213
Loss from discontinued operations, net of tax	(705)	329	[1]	(513)	[1]	(289)	[1]	(248)	[1]	0	0	0	(1,178)	(248)	[3]	0
Net earnings for basic earnings per share													221,474	248,126	[3]	230,213
Interest associated with convertible notes, net of tax													0	935	[3]	3,585
Net earnings available to common shareholders - diluted													$ 221,474	$ 249,061	[3]	$ 233,798
Denominator for earnings per share:
Weighted average number of common shares outstanding													158,323	156,141	[3]	149,405
Assumed exercise of stock options and vesting of restricted stock awards, net of shares assumed reacquired under the treasury stock method													2,528	3,196	[3]	3,518
Assumed conversion of convertible notes													0	2,293	[3]	8,646
Diluted shares outstanding													160,851	161,630	[3]	161,569
Anti-dilutive shares of stock-based compensation awards excluded													352	418		515

[1] Amounts for the fourth quarter of 2010 and the first three quarters of 2011 have been adjusted for the reclassification of certain discontinued operations to continuing operations.

[2] Earnings from continuing operations for the second quarter of 2011 include the payment of a $39 million litigation settlement. See Note 13 to the Consolidated Financial Statements for additional information.

[3] Amounts have been adjusted for the reclassification of certain discontinued operations to continuing operations.