Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2016

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 March 31,
		2016			2015
	(In millions)
Total stock-based compensation expense:
Equity classified awards expense		$	3.2		$	2.4
Liability classified awards expense		0.8			0.3
Total pre-tax stock-based compensation expense		4.0			2.7
Book income tax benefit		(1.5		)	(1.0		)
Total stock-based compensation expense, net of tax		$	2.5		$	1.7

Schedule of stock option valuation assumptions

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

Risk-free interest rate	1.08	%
Weighted average historical volatility	27.1	%
Dividend yield	4.05	%
Expected years until exercise	4.5
Weighted average fair value of options granted	$13.55

Schedule of stock option activity

Stock option balances as of March 31, 2016 and related activity for the three months ended March 31, 2016 were as follows:

	Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (in Years)	Aggregate Intrinsic Value (in Millions)
Outstanding at December 31, 2015	504,462		$	69.99
Granted	255,825		90.90
Exercised	(36,005	)	24.43
Outstanding at March 31, 2016	724,282		79.64		7.9	$12.1
Vested at March 31, 2016 and Expected to Vest	659,693		78.24		7.7	$11.9
Exercisable at March 31, 2016	355,330		$	64.44	6.1	$11.0

Schedule of restricted stock unit activity

Outstanding balances as of March 31, 2016 and activity related to restricted stock and restricted stock units for the three months ended March 31, 2016 were as follows:

	Restricted Stock		Weighted Average Grant Date Fair Value		Restricted Stock Units		Weighted Average Grant Date Fair Value
Outstanding at December 31, 2015	257,594		$	89.99	35,116		$	86.30
Granted	72,674		90.76		11,961		90.90
Released	(53,847	)	73.66		(14,027	)	72.01
Forfeited	(7,794	)	89.93		—		—
Outstanding at March 31, 2016	268,627		$	93.48	33,050		$	93.97