Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2018

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

Components of the Company’s stock-based compensation expense

The following table summarizes the components of stock-based compensation expense included in general and administrative expenses in the Consolidated Statements of Comprehensive Income:

	Three months ended June 30,						Six months ended June 30,
	2018			2017			2018			2017
	(In millions)
Total stock-based compensation expense:
Equity classified awards expense	$	2.3		$	1.5		$	5.7		$	7.7
Liability classified awards expense (credit)	0.4			(1.3		)	0.9			(1.1		)
Total pre-tax stock-based compensation expense	2.7			0.2			6.6			6.6
Book income tax benefit	(0.7		)	(0.1		)	(1.7		)	(2.5		)
Total stock-based compensation expense, net of tax	$	2.0		$	0.1		$	4.9		$	4.1

Schedule of stock option valuation assumptions

The following summarizes the assumptions used in estimating the fair values:

Risk-free interest rate	2.4	%
Weighted average historical volatility	33.0	%
Dividend yield	3.7	%
Expected years until exercise	3.0
Weighted average fair value of options granted	$9.79
Weighted average fair value of restricted stock units granted	$34.53

The following summarizes the assumptions used in the Black-Scholes model:

Risk-free interest rate	2.6	%
Weighted average historical volatility	26.1	%
Dividend yield	3.6	%
Expected years until exercise	4.6
Weighted average fair value of options granted	$11.94

Schedule of stock option activity

Stock option balances at June 30, 2018, and activity for the six months ended June 30, 2018 were as follows:

	Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in Years)	Aggregate Intrinsic Value (in Millions)
Outstanding at December 31, 2017	1,272,048		$	61.44
Granted	248,899		69.12
Exercised	(12,460	)	49.75
Outstanding at June 30, 2018	1,508,487		62.81		7.0	$	24.6
Vested at June 30, 2018 and Expected to Vest	1,323,639		64.44		6.6	$	20.2
Exercisable at June 30, 2018	634,238		$	75.29	3.9	$	5.8

Schedule of restricted stock unit activity

Outstanding balances as of June 30, 2018, and activity related to restricted stock and restricted stock units for the six months ended June 30, 2018 were as follows:

	Restricted Stock		Weighted Average Grant Date Fair Value		Restricted Stock Units		Weighted Average Grant Date Fair Value
Outstanding at December 31, 2017	275,191		$	65.81	303,348		$	28.39
Granted	90,078		68.89		52,711		48.13
Released	(52,342	)	87.69		(15,737	)	98.54
Forfeited	(12,816	)	61.16		(71	)	53.49
Outstanding at June 30, 2018	300,111		$	63.13	340,251		$	27.70