Share-Based Compensation Plans (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Expenses Associated with Share-Based Compensation Plans

The following table summarizes the costs associated with the Company’s share-based compensation plans:

	Year ended December 31,
	2017		2016		2015
	(in thousands)
Expense:
RSUs	$	34,059	$	31,120	$	21,761
Stock options		263		271		271
Employee stock purchase plan		3,077		2,734		2,307
	$	37,399	$	34,125	$	24,339

Summary of RSU Activity

The following table summarizes RSU activity for the year ended December 31, 2017:

(in thousands, except weighted-average grant-date fair value)	Shares			Weighted-average grant-date fair value
Unvested at December 31, 2016	1,510		$	33.38
Granted during 2017	930			39.56
Vested during 2017	(1,016	)		34.47
Forfeited during 2017	(13	)		35.47
Unvested at December 31, 2017	1,411		$	36.66

Summary of Stock Option Activity

The following table summarizes stock option activity for the year ended December 31, 2017:

(in thousands, except weighted-average exercise price and contractual term)	Number outstanding			Weighted- average exercise price		Weighted- average remaining contractual term		Aggregate intrinsic value
Balance at December 31, 2016		132		$	27.66
Exercised during 2017		(66	)		27.66
Balance at December 31, 2017		66		$	27.66		6.0 years	$	1,883
Vested and expected to vest at December 31, 2017		66		$	27.66		6.0 years	$	1,883
Exercisable at December 31, 2017		66		$	27.66		6.0 years	$	1,883