Stock-Based Compensation Plans (Tables)

12 Months Ended

Dec. 31, 2015

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

Schedule of Share-based Compensation, Stock Options, Activity

A summary of option activity under the Omnibus Plan as of December 31, 2015 and changes during the year then ended is presented below:

	Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at beginning of year	983,280		$	76.99
Granted	360,235		79.67
Exercised	(118,628	)	45.74
Expired	(4,171	)	87.49
Forfeited	(17,681	)	94.97
Outstanding at end of year	1,203,035		$	80.58	3.0	$	311
Vested or expected to vest at end of year	1,199,470		$	80.57	3.0	$	311
Exercisable at end of year	566,815		$	73.28	1.9	$	311

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions

The following weighted average assumptions were used to estimate the grant date fair value of options granted during the years ended December 31, 2015, 2014 and 2013 using the Black-Scholes option pricing model:

	2015		2014		2013
Expected volatility	27	%	22	%	29	%
Expected term (in years)	4		4		4
Risk-free interest rate	1.31	%	1.20	%	0.89	%
Expected dividend yield	0	%	0	%	0	%

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity

The following table summarizes the Company's non-vested restricted stock outstanding as of December 31, 2015 and changes during the year then ended:

	Shares		Weighted Average Grant Date Fair Value
Non-vested at beginning of year	124,239		$	90.54
Granted	95,092		$	79.30
Vested	(61,741	)	$	84.82
Forfeited	(2,789	)	$	94.89
Non-vested at end of year	154,801		$	85.84

Schedule of Share-based Compensation, Restricted Stock Units Award Activity

The following table summarizes the Company's non-vested restricted stock units outstanding as of December 31, 2015 and changes during the year then ended:

	Shares		Weighted Average Grant Date Fair Value
Non-vested at beginning of year	65,406		$	83.55
Granted	44,761		$	70.64
Vested	(56,786	)	$	74.56
Forfeited	(5,673	)	$	88.68
Non-vested at end of year	47,708		$	81.52

Share-based Compensation, Performance Shares Award Unvested Activity

The following table summarizes the performance-based restricted stock units at the maximum award amounts as of December 31, 2015 and changes during the year then ended. Actual shares that will vest depending on the level of attainment of the performance-based criteria:

	Shares	Weighted Average Grant Date Fair Value
Non-vested at beginning of year	14,424	$	42.39
Granted	14,386	$	62.73
Vested	—	$	—
Forfeited	—	$	—
Non-vested at end of year	28,810	$	52.55

Schedule of Performance-based Units Fair Value Assumptions

The following assumptions were used to estimate the grant date fair value of the performance-based restricted stock units granted during the years ended December 31, 2015 and 2014 and using the Monte Carlo simulation model:

	2015		2014
Volatility of the Company's common stock	24	%	25	%
Average volatility of peer group and S&P 500 companies	25	%	29	%
Average correlation coefficient of peer group and S&P 500 companies	0.5		0.6
Risk-free interest rate	0.98	%	0.81	%
Expected dividend yield	0	%	0	%
Expected term (in years)	3		3