Earnings Per Share (Tables)

9 Months Ended

Sep. 30, 2013

Earnings Per Share [Abstract]

Earnings Per Share Summary

	Three Months Ended September 30,				Nine Months Ended September 30,
($ thousands, except share and per share data)	2013		2012		2013		2012
Numerator
Net income attributable to common stockholders	$	13,036	$	45,080	$	77,353	$	134,950
Less: income allocated to participating securities		(41)		(188)		(276)		(702)
Net income attributable to common stockholders - basic and diluted	$	12,995	$	44,892	$	77,077	$	134,248
Denominator
Weighted average common shares outstanding - basic		88,109,088		89,947,641		87,919,351		89,592,430
Plus: dilutive effect of stock options and unvested restricted stock units		798,725		902,313		970,970		1,079,586
Weighted average common shares outstanding - diluted		88,907,813		90,849,954		88,890,321		90,672,016
Net income attributable per common share:
Basic	$	0.15	$	0.50	$	0.88	$	1.50
Diluted	$	0.15	$	0.49	$	0.87	$	1.48