Share-based Compensation (Tables)

3 Months Ended

Mar. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

The following table summarizes the Company’s stock option activity (in thousands, except per share data and years) for the three months ended March 31, 2018:

	Stock Options Outstanding
				Weighted Average		Aggregate		Weighted Average
				Exercise Price		Intrinsic		Remaining Contractual
	Shares			Per Share		Value		Term (Years)
Balance as of January 1, 2018		992		$	145.28
Granted		475			131.71
Exercised		0			0.00	$	0
Forfeited/Expired		(4	)		165.01
Balance as of March 31, 2018		1,463		$	140.83
Exercisable as of March 31, 2018		587		$	138.98	$	3,029		6.5
Expected to vest as of March 31, 2018		876		$	142.06		1,085		8.8
Total		1,463		$	140.83	$	4,114		7.9

Schedule of Range of Exercise Prices per Share

Stock options outstanding as of March 31, 2018 are comprised of the following range of exercise prices per share (in thousands, except per share data and years):

	Stock Options Outstanding at March 31, 2018
			Weighted Average		Weighted Average
			Exercise Price		Remaining Contractual
Range of Exercise Prices per Share	Shares		Per Share		Term (Years)
$117.85 - $120.00		25	$	118.55		6.1
$120.01 - $150.00		1,045	$	126.78		8.0
$150.01 - $180.00		198	$	167.55		6.9
$180.01 - $201.25		195	$	191.78		8.4
Total		1,463	$	140.83		7.9

Assumptions Used in Black-Scholes Pricing Model

The weighted average grant date fair value of stock option awards using the Black-Scholes pricing model was $52.44 and $77.31 for each share subject to a stock option granted during the three months ended March 31, 2018 and 2017, respectively, based on the following assumptions:

	Three months ended
	March 31,
	2018			2017
Expected term of options in years	6.3			6.3
Expected volatility	35.2 - 35.5%				37.8	%
Risk-free interest rate		2.7	%		2.3	%
Expected dividend yield		0.0	%	0.0%