Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2019

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

Summary of Stock-based Compensation Expense

Stock-based compensation expense is summarized as follows:

	Three Months Ended March 31,
	2019		2018
($ in thousands)
Stock-based compensation expense	$	5,629	$	5,909

Summary of Restricted Stock Units Activity

RSU activity for the three months ended March 31, 2019 is summarized as follows:

	Number of Shares		Weighted Average Grant Date Fair Value
Outstanding at December 31, 2018	552,238		$	111.49
Granted	147,369		$	108.03
Forfeited	(11,993	)	$	77.21
Settled	(126,081	)	$	96.57
Outstanding at March 31, 2019	561,533		$	114.67

Summary of Stock Option Activity

Stock option activity for the three months ended March 31, 2019 is summarized as follows:

	Number of Shares		Weighted Average Exercise Price
Outstanding at December 31, 2018	76,751		$	12.86
Exercised	(55,106	)	$	9.52
Outstanding, vested and exercisable at March 31, 2019	21,645		$	21.37