Net Income per Share (Tables)

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Computation of basic and diluted earnings per common share

The following table sets forth the computation of basic and diluted earnings per common share:

	Year Ended December 31,
	2017		2016		2015
	(in thousands, except per share amounts)
Numerator:
Net income (1)	$	420,606	$	264,879	$	317,220
Denominator:
Weighted-average shares outstanding, basic	69,221		70,344		72,208
Effect of dilutive stock awards	156		164		218
Adjusted weighted-average shares outstanding, diluted	69,377		70,508		72,426
Net Income per Share:
Basic earnings per common share (1)	$	6.08	$	3.77	$	4.39
Diluted earnings per common share (1)	$	6.06	$	3.76	$	4.38
Anti-dilutive weighted-average shares	85		66		52