Stock Based Compensation (Tables)

3 Months Ended

Mar. 31, 2016

Stock Based Compensation [Abstract]

Stock Based Compensation Expense

The following table provides information regarding the Company's stock-based compensation expense (in thousands):

	Three months ended March 31,
	2016			2015
Stock based compensation		$	18,979		$	13,801
Tax effect recognized in net income			6,643			4,830
Windfall tax benefit, net			-			4,107

Windfall tax benefits are no longer calculated due to the adoption of the ASU related to stock compensation (see Note 2), as all tax benefits are recognized in net income.

Weighted average assumptions used to value option grants

	Three Months Ended March 31,
	2016		2015
Risk-free interest rate (%)		1.41		1.51
Expected option life (years)		5.20		5.10
Expected volatility (%)		21.63		22.28
Expected dividend yield (%)		0.70		0.63