Share-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2018

Share-based Compensation

Summary of share-based compensation expense

	Three months ended			Six months ended
	June 30,			June 30,
(in thousands)	2018		2017	2018		2017
Share-based compensation	$	14,229	11,008	$	20,524	20,055

Summary of weighted average assumptions, and weighted average fair value of options

		Six months ended
		June 30,
	2018			2017
Number of options granted		360,118		548,265
Weighted average exercise price	$	86.90		54.90
Risk-free interest rate		2.55	%	1.78	%
Expected volatility		21.80	%	21.71	%
Expected term (years)		4.8		4.6
Dividend yield		0.60	%	0.73	%
Weighted average fair value	$	19.23		10.83

Nonvested Share Awards

Share-based Compensation

Summary of shares granted

		Six months ended June 30,
	2018		2017
Number of shares granted		320,853	322,926
Market value (in millions)	$	28.6	17.6

Market Based Share Awards

Share-based Compensation

Summary of shares granted

Year Awarded	Performance Period Ending	Performance Measure	Number of Shares Granted	Period Expensed Through
2018	December 2020	TSR	33,940	December 2020
2017	December 2019	TSR	44,275	December 2019