Earnings per Share (Reconciliation of Denominator for Basic and Diluted Earnings Per Share) (Details) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings Per Share [Abstract]
Weighted average common shares—basic	132,538,123	133,223,705	132,625,857	133,148,398
Plus incremental shares from: Assumed exercise of options	506,852	544,185	498,840	542,438
Weighted average common shares-diluted	133,044,975	133,767,890	133,124,697	133,690,836
Earnings per share: Basic (usd per share)	$ 1.55	$ 1.27	$ 2.65	$ 2.45
Earnings per share: Diluted (usd per share)	$ 1.54	$ 1.26	$ 2.64	$ 2.44