Earnings Per Share (Computation Of Basic And Diluted Earnings Per Share ) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Abstract]
Income from continuing operations	$ 45,488	$ 40,093	$ 45,577	$ 47,973	$ 52,126	$ 74,929	$ 30,916	$ 14,936	$ 179,130	$ 172,907	$ 145,296
Income/(loss) from discontinued operations	(306)	(190)	(1,976)	(591)	(3,857)	(5,239)	(1,481)	(317)	(3,063)	(10,894)	(6,723)
Net income	$ 45,182	$ 39,903	$ 43,601	$ 47,382	$ 48,269	$ 69,690	$ 29,435	$ 14,619	$ 176,067	$ 162,013	$ 138,573
Average shares used in basic computation	66,851	66,691	66,302	66,037	64,859	64,706	64,505	60,054	66,472	63,568	53,563
Dilutive effect of stock options and units									9,904	9,936	9,374
Average shares used in diluted computation	77,540	76,681	75,641	75,691	75,495	75,191	74,090	69,189	76,376	73,504	62,937
Income from continuing operations	$ 0.67	$ 0.60	$ 0.69	$ 0.73	$ 0.80	$ 1.16	$ 0.48	$ 0.25	$ 2.69	$ 2.72	$ 2.71
Loss from discontinued operations			$ (0.03)	$ (0.01)	$ (0.06)	$ (0.08)	$ (0.02)	$ (0.01)	$ (0.04)	$ (0.17)	$ (0.12)
Earnings per basic common share	$ 0.67	$ 0.60	$ 0.66	$ 0.72	$ 0.74	$ 1.08	$ 0.46	$ 0.24	$ 2.65	$ 2.55	$ 2.59
Income from continuing operations	$ 0.59	$ 0.52	$ 0.60	$ 0.63	$ 0.69	$ 1.00	$ 0.42	$ 0.22	$ 2.35	$ 2.35	$ 2.31
Loss from discontinued operations	$ (0.01)		$ (0.02)		$ (0.05)	$ (0.07)	$ (0.02)	$ (0.01)	$ (0.04)	$ (0.15)	$ (0.11)
Earnings per diluted common share	$ 0.58	$ 0.52	$ 0.58	$ 0.63	$ 0.64	$ 0.93	$ 0.40	$ 0.21	$ 2.31	$ 2.20	$ 2.20