Stock Compensation Plans (Tables)

3 Months Ended

12 Months Ended

Mar. 31, 2016

Dec. 31, 2015

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Weighted Average Fair Value of Options Granted

The fair value of each option grant is estimated on the date of grant using the Black-Scholes option-pricing model with the following weighted-average assumptions used:

Grant Year	Dividend Yield			Expected Volatility			Risk Free Interest Rate			Expected Lives
2015		5	%		45	%		2	%		6
2014		2	%		48	%		1	%		6
2013		0	%		51	%		1	%		6

Stock Option Transactions under Various Stock-Based Employee Compensation Plans

Information regarding the 1996 Plan for the year ended December 31, 2015 is as follows:

	Shares			Weighted Average Exercise Price		Weighted Average Contractual Life
Outstanding, beginning of year		2,774,591		$	33.76
Granted		42,000			55.52
Exercised		(881,936	)		26.50
Forfeited		(8,600	)		48.93
Expired		—			—
Outstanding, end of year		1,926,055			37.49		6.22
Exercisable at end of year		1,146,455			33.59		5.56

Summary of ESPP Share Activity

The following is a summary of 2009 ESPP share activity for the period ended March 31, 2016:

	Shares
Available for future purchases, January 1, 2016		279,589
Additional shares reserved under 2009 ESPP		82,084
Purchases		(33,923	)
Available for future purchases, March 31, 2016		327,750

The following is a summary of 2009 ESPP share activity for the year ended December 31, 2015:

	Shares
Available for future purchases, January 1, 2015		307,448
Additional shares reserved under 2009 ESPP		80,933
Purchases		(108,792	)
Available for future purchases, December 31, 2015		279,589