Stock Compensation Plans (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of stock compensation expense and related net tax benefits

The following table presents a summary of the total share-based compensation expense and the related net tax benefits associated with the Company’s various employee share-based compensation plans for the years ended December 31, 2018, 2017 and 2016:

($ in thousands)	Year Ended December 31,
	2018		2017		2016
Stock compensation costs	$	30,937	$	24,657	$	22,102
Related net tax benefits for stock compensation plans	$	5,089	$	4,775	$	1,055

Summary of activities for time-based and performance-based restricted stock units

The following table presents a summary of the activities for the Company’s time-based and performance-based RSUs for the year ended December 31, 2018. The number of outstanding performance-based RSUs stated below assumes the associated performance targets will be met at the target level.

	Year Ended December 31, 2018
	Time-Based RSUs				Performance-Based RSUs
	Shares		Weighted- Average Grant Date Fair Value		Shares		Weighted- Average Grant Date Fair Value
Outstanding, beginning of year	1,166,580		$	42.00	424,299		$	41.44
Granted	427,805		66.86		120,286		70.13
Vested	(349,939	)	39.84		(133,295	)	41.15
Forfeited	(123,055	)	50.48		—		—
Outstanding, end of year	1,121,391		$	51.22	411,290		$	49.93