Capital Stock (Summary of Common Stock Activity) (Details) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common shares outstanding at beginning of period	139,000,471	138,207,889	143,136,473
Shares repurchased	(165,138)	(36,702)	(6,925,789)
Shares issued upon exercise of employee stock options	207,890	744,431	855,061
Restricted stock issued to employees, net of forfeitures	375,575	60,933	1,115,484
Shares issued to non-employee directors	22,500	23,920	26,660
Common shares outstanding at end of period	139,441,298	139,000,471	138,207,889