Earnings Per Share (Tables)

6 Months Ended

Jun. 30, 2013

Earnings (Loss) Per Share [Abstract]

Earnings Per Share Summary

	Three Months Ended June 30,				Six Months Ended June 30,
($ thousands, except share and per share data)	2013		2012		2013		2012
Numerator
Net income attributable to common stockholders	$	35,356	$	61,524	$	64,317	$	89,870
Less: income allocated to participating securities		(127)		(330)		(243)		(514)
Net income attributable to common stockholders - basic and diluted	$	35,229	$	61,194	$	64,074	$	89,356
Denominator
Weighted average common shares outstanding - basic		87,864,761		89,519,166		87,822,911		89,412,872
Plus: dilutive effect of stock options and unvested restricted stock units		972,367		1,094,430		945,162		1,137,091
Weighted average common shares outstanding - diluted		88,837,128		90,613,596		88,768,073		90,549,963
Net income attributable per common share:
Basic	$	0.40	$	0.68	$	0.73	$	1.00
Diluted	$	0.40	$	0.68	$	0.72	$	0.99