Net Income Per Common Share (Tables)

12 Months Ended

Dec. 31, 2016

Earnings Per Share [Abstract]

Computation of net income per common share

	2016		2015		2014
Basic
Average common shares outstanding	91,838,603		92,197,207		96,190,101
Net income	$	1,132,703	$	1,053,849	$	865,887
Net income per common share	$	12.33	$	11.43	$	9.00
Diluted
Average common shares outstanding	91,838,603		92,197,207		96,190,101
Stock options and other contingently issuable shares (1)	2,089,921		1,826,885		1,885,334
Non-vested restricted stock grants	559,562		519,451		665,086
Average common shares outstanding assuming dilution	94,488,086		94,543,543		98,740,521
Net income	$	1,132,703	$	1,053,849	$	865,887
Net income per common share	$	11.99	$	11.15	$	8.77

⁽¹⁾  Stock options and other contingently issuable shares excludes 62,935, 34,463 and 608,477 shares at December 31, 2016, 2015 and 2014, respectively, due to their anti-dilutive effect.