Stock-Based Compensation (Q3) (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2018

Dec. 31, 2017

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

The following table summarizes the Company’s stock option activity and related information for the 2011 Plan, the 2000 Plan and the Directors Plan for the nine months ended September 30, 2018:



	Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life		Aggregate Intrinsic value (in thousands)
Outstanding at December 31, 2017		983,512		$	40.62		4.0	$	40,137
Granted		82,580			77.54				2,258
Exercised		(574,303	)		23.88				46,520
Canceled		(16,471	)		64.46				666
Outstanding at September 30, 2018		475,318			56.50		5.9		22,997
Exercisable at September 30, 2018		291,169			49.75		5.0		16,051

The following table summarizes the Company’s stock option activity and related information for the 2011 Plan, the 2000 Plan and Directors Plan for the years ended December 31:

	Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life		Aggregate Intrinsic value (in thousands)
Outstanding at December 31, 2014		1,147,558		$	28.33		5.5	$	67,205
Granted		84,675			87.35				1,375
Exercised		(124,156	)		26.70				(5,516	)
Canceled		(10,754	)		65.22				(64	)
Outstanding at December 31, 2015		1,097,323		$	32.70		4.8	$	42,154
Granted		94,115			61.39				2,035
Exercised		(83,790	)		25.58				(4,813	)
Canceled		(8,825	)		71.47				(102	)
Outstanding at December 31, 2016		1,098,823		$	35.39		4.3	$	52,332
Granted		65,522			86.91				—
Exercised		(166,838	)		21.37				(10,020	)
Canceled		(13,995	)		76.89				(64	)
Outstanding at December 31, 2017		983,512		$	40.62		4.0	$	40,137
Exercisable at December 31, 2017		802,609		$	32.52		3.3	$	36,848

Share-Based Fair Value of Each Option Grant Weighted-Average Assumptions

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:



	Nine Months Ended September 30,
	2018			2017
Dividend yield		0.31	%		0.23	%
Risk-free interest rate		2.78	%		2.17	%
Stock price volatility		23.9	%		23.4	%
Expected life (years)		5.0			5.0

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:

	For the year ended December 31,
	2017			2016			2015
Dividend yield		0.23	%		0.26	%		0.14	%
Risk-free interest rate		2.2	%		1.5	%		1.8	%
Stock price volatility		23.4	%		26.9	%		27.3	%
Expected life (years)		5.0			5.0			5.0
Weighted average fair value of options granted during the year	$	20.69		$	14.96		$	24.41

Restricted Stock Activity and Incentive Stock Awards Activity

The following table summarizes the restricted stock activity and related information for the 2011 Plan, the 2000 Plan and the Directors Plan, and incentive stock units activity for the 2011 Plan and the 2000 Plan with related information for the nine months ended September 30, 2018:



	Restricted Stock and Units			Incentive Stock Units			Weighted Average Grant Date Fair Value
Outstanding at December 31, 2017		399,000			327,333		$	78.76
Granted		223,990			175,100			73.76
Vested		(143,327	)		(93,312	)		81.42
Adjustment for incentive stock awards expected to vest		—			(3,934	)		73.40
Canceled		(28,643	)		(25,775	)		78.80
Outstanding at September 30, 2018		451,020			379,412			75.62