Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2016

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

Schedule of Share-based Compensation, Stock Options, Activity

A summary of stock option transactions and related information for the year ended December 31, 2016 is presented below:

	Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
Outstanding as of January 1, 2016	1,089,538		$	44.95
Granted	155,100		$	68.73
Exercised	(487,203	)	$	39.44
Forfeited	(9,064	)	$	64.20
Outstanding as of December 31, 2016	748,371		$	53.24	7.1	$	37,523
Exercisable as of December 31, 2016	384,679		$	45.82	5.6	$	22,142

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

The fair value of each option was estimated using the following assumptions:

	2016		2015		2014
Expected volatility	27.58% - 27.70%		27.95% - 28.00%		27.96% - 28.32%
Dividend yield	0.00	%	0.00	%	0.00	%
Expected option life - years	6.0		6.0		6.0
Risk-free rate	1.1% - 1.4%		1.5% - 1.7%		1.9% - 2.0%

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

A summary of restricted common stock and restricted common units transactions and related information for the year ended December 31, 2016 is presented below:

	Restricted Common Stock and Restricted Common Units		Weighted Average Grant Date Fair Value
Non-vested as of January 1, 2016	378,746		$	53.56
Granted	153,818		$	70.09
Vested	(133,564	)	$	41.79
Forfeited	(27,441	)	$	62.39
Non-vested as of December 31, 2016	371,559		$	63.98

Schedule of Nonvested Performance-based Units Activity [Table Text Block]

A summary of performance units transactions and related information for the year ended December 31, 2016 is presented below:

	Performance Units		Weighted Average Grant Date Fair Value
Non-vested as of January 1, 2016	172,400		$	60.97
Granted	86,150		$	68.71
Forfeited	(10,583	)	$	63.87
Non-vested as of December 31, 2016	247,967		$	63.53

Schedule of Share-based Payment Award, TSRs, Valuation Assumptions [Table Text Block]

The fair value of the TSR-based performance grant was estimated using the following assumptions:

	2016
Expected volatility	27.60	%
Dividend yield	0.00	%
Expected life - years	3
Risk-free rate	0.87	%