Net Income Per Common Share (Tables)

12 Months Ended

Dec. 31, 2013

Earnings Per Share [Abstract]

Computation of net income per common share

	2013			2012			2011
Basic
Average common shares outstanding	100,897,512			101,714,901			103,471,323
Net income	$	752,561		$	631,034		$	441,860
Less net income allocated to unvested restricted shares	(4,596		)	(5,114		)	(4,825		)
Net income allocated to common shares	$	747,965		$	625,920		$	437,035
Net income per common share	$	7.41		$	6.15		$	4.22
Diluted
Average common shares outstanding	100,897,512			101,714,901			103,471,323
Stock options and other contingently issuable shares (a)	2,151,359			2,215,528			2,200,650
Average common shares outstanding assuming dilution	103,048,871			103,930,429			105,671,973
Net income	$	752,561		$	631,034		$	441,860
Less net income allocated to unvested restricted shares assuming dilution	(4,509		)	(5,008		)	(4,756		)
Net income allocated to common shares assuming dilution	$	748,052		$	626,026		$	437,104
Net income per common share	$	7.26		$	6.02		$	4.14

(a) Stock options and other contingently issuable shares excludes 842,354, 1,047,734 and 101,260 shares at December 31, 2013, 2012 and 2011, respectively, due to their anti-dilutive effect.