Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2019

Share-based Payment Arrangement [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,
	2019			2018			2019			2018
	(In millions)
Total stock-based compensation expense:
Equity classified awards expense	$	1.8		$	2.3		$	5.9		$	5.7
Liability classified awards expense	1.4			0.4			2.4			0.9
Total pre-tax stock-based compensation expense	3.2			2.7			8.3			6.6
Book income tax benefit	(0.9		)	(0.7		)	(2.2		)	(1.7		)
Total stock-based compensation expense, net of tax	$	2.3		$	2.0		$	6.1		$	4.9

Schedule of stock option valuation assumptions

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

Risk-free interest rate	2.5	%
Weighted average historical volatility	30.3	%
Dividend yield	2.8	%
Expected years until exercise	4.7
Weighted average fair value of options granted	$21.93

Schedule of stock option activity

Stock option balances at June 30, 2019, and activity for the six months ended June 30, 2019 were as follows:

	Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in Years)	Aggregate Intrinsic Value (in Millions)
Outstanding at December 31, 2018	1,439,708		$	63.21
Granted	132,832		98.97
Exercised	(118,991	)	58.32
Forfeited	(77,952	)	69.54
Outstanding at June 30, 2019	1,375,597		66.72		6.0	$	41.3
Vested at June 30, 2019 and Expected to Vest	1,263,536		67.54		5.7	$	36.9
Exercisable at June 30, 2019	684,738		$	75.93	3.4	$	14.7

Schedule of restricted stock unit activity

Outstanding balances as of June 30, 2019, and activity related to restricted stock and restricted stock units for the six months ended June 30, 2019 were as follows:

	Restricted Stock		Weighted Average Grant Date Fair Value		Stock-Settled Restricted Stock Units		Weighted Average Grant Date Fair Value
Outstanding at December 31, 2018	267,242		$	63.97	374,529		$	31.05
Granted	68,376		97.74		16,232		98.97
Released	(58,885	)	81.19		(12,293	)	90.34
Forfeited	(23,437	)	66.50		(27,802	)	34.53
Outstanding at June 30, 2019	253,296		$	68.84	350,666		$	30.66

Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]

The Company has granted cash-settled restricted stock units to certain employees. These instruments are recorded as liabilities at fair value as of the respective period end.

	Cash-Settled Restricted Stock Units		Weighted Average Grant Date Fair Value
Outstanding at December 31, 2018	53,766		$	94.45
Granted	20,249		96.12
Released	(317	)	82.16
Forfeited	(4,054	)	98.35
Outstanding at June 30, 2019	69,644		$	98.59