Shareholder's Equity (Schedule of Stock Option Activity (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at beginning of period, Number of Shares	270,464	1,662,830	2,510,054
Options exercised, Number of Shares	(111,743)	(1,392,366)	(841,599)
Options terminated, Number of Shares			(5,625)
Outstanding at end of period, Number of Shares	158,721	270,464	1,662,830	2,510,054
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Outstanding at beginning of period, Weighted Average Exercise Price (usd per share)	$ 23.16	$ 23.82	$ 23.09
Options exercised, Weighted Average Exercise Price (usd per share)	$ 23.53	$ 23.95	$ 21.64
Options terminated, Weighted Average Exercise Price (usd per share)			$ 21.85
Outstanding at end of period, Weighted Average Exercise Price (usd per share)	$ 22.89	$ 23.16	$ 23.82	$ 23.09
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Outstanding at beginning of period, Weighted Average Remaining Contractual Life (in years)	1 year 256 days	2 years 6 months 0 days	2 years 329 days	3 years 146 days
Outstanding at end of period, Weighted Average Remaining Contractual Life (in years)	1 year 256 days	2 years 6 months 0 days	2 years 329 days	3 years 146 days