Earnings Per Common Share (Tables)

3 Months Ended

Mar. 31, 2012

Earnings Per Common Share [Abstract]

Earnings per share

	Three Months Ended
	March 31,
	2012		2011
Numerator:
Net income	$	56,218	$	48,260
Denominator:
Denominator for basic earnings per common share -weighted average shares		63,881		68,565
Effect of dilutive securities:
Employee stock-based compensation		1,803		2,306
Denominator for diluted earnings per common share -adjusted weighted average shares		65,684		70,871
Basic earnings per common share	$	0.88	$	0.70
Diluted earnings per common share	$	0.86	$	0.68