Share-based Compensation (Tables)

6 Months Ended

Jun. 30, 2017

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 June 30, 2017:

	Stock Options Outstanding
				Weighted Average		Aggregate		Weighted Average
				Exercise Price		Intrinsic		Remaining Contractual
	Shares			Per Share		Value		Term (Years)
Balance as of April 1, 2017		939		$	146.27
Granted		25			182.64
Exercised		(5	)		119.02	$	329
Forfeited/Expired		(10	)		201.25
Balance as of June 30, 2017		949		$	146.79
Exercisable as of June 30, 2017		514		$	133.39	$	30,133	7.1
Expected to vest as of June 30, 2017		435		$	162.64		13,130	8.1
Total		949		$	146.79	$	43,263	7.5

Schedule of Range of Exercise Prices per Share

Stock options outstanding as of June 30, 2017 are comprised of the following range of exercise prices per share (in thousands, except per share data and years):

	Stock Options Outstanding at June 30, 2017
			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	6.8
$120.01 - $150.00		510	$	121.43	6.8
$150.01 - $180.00		209	$	167.41	7.7
$180.01 - $201.25		205	$	192.24	9.1
Total		949	$	146.79		7.5

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 $72.78 and $75.54 for each share subject to a stock option granted during the three months ended June 30, 2017 and 2016, respectively, based on the following assumptions:

	Three months ended
	June 30,
	2017			2016
Expected term of options in years	6.3			6.3
Expected volatility		37.4	%	38.5%
Risk-free interest rate		1.9	%	1.4 - 1.6%
Expected dividend yield		0.0	%	0.0%