Shareholders' Equity (Narrative) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	6 Months Ended	57 Months Ended	0 Months Ended
	Jun. 30, 2013	Jun. 30, 2013	Feb. 19, 2013 Accelerated Share Repurchase Transaction [Member]	Nov. 20, 2012 Accelerated Share Repurchase Transaction [Member]
Acquisition of treasury stock (shares)	270	3,993	22	65
Acquisition of treasury stock (value)	$ 80,612	$ 580,715
Stock repurchase program, authorized amount	700,000			25,000
Percentage of treasury shares acquired				70.00%
Weighted-average price per share			$ 287.20
Value of common shares remaining to be repurchased	119,575
Advance payment under agreement				$ 25,000