Share-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2017

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

Summary of awards granted during the period

Awards granted during the first six months of 2017, weighted average fair value, and assumptions used to determine fair value were as follows:

	MSUs			Performance Shares			RSUs
Awards granted	371,346			112,732			49,000
Weighted average fair value (a)	$	35.79		$	39.42		$	31.36
Expected volatility (b)	32.10		%	32.10		%	N/A
Risk-free rate (c)	1.39		%	1.39		%	N/A
Expected term (in years) (d)	2.96			2.96			N/A
Expected dividends	—			—			N/A

(a) Fair value of MSUs and Performance Shares is estimated on the date of grant using the Monte Carlo simulation using the assumptions outlined above. Fair value of RSUs is equal to the closing price of our common stock on the date of grant.

(b) The expected volatility rate is based on stock price history immediately prior to grant for a period commensurate with the expected term.

(c) The risk-free rate is based on zero coupon U.S. government issues at the time of grant.

(d) The expected term represents the period from the valuation date to the end of the performance period.

Terms of the awards granted during the first six months of 2017 were as follows:

	MSUs	Performance Shares	RSUs
Maximum shares/units earned	Varies from 0% to 150% of the number of MSUs awarded depending on the actual performance of our stock price	Varies from 0% to 200% of the number of performance shares awarded depending on the performance of our total stockholder return relative to the performance of the Dow Jones U.S. Construction and Materials Index (a)	100%
Vesting Provisions	Three-year performance period	Three-year performance period	Specified number of years from the grant date
Vesting in the case of termination of employment due to death, disability, retirement or change in control during performance period (b)	Pro-rated based on the number of full months employed in 2017 with awards issued at the end of the three-year period	Pro-rated based on the number of full months employed during the performance period with awards issued at the end of the three-year period	Varies
Settlement	Settled in common stock at the end of the performance or vesting period

(a) Adjustments to the performance of the Dow Jones U.S. Construction and Materials Index may be made in certain circumstances.

(b) Early vesting for MSUs, performance shares and RSUs in situations where there is a change in control also requires a related loss of employment or diminution of duties.

Schedule of antidilutive securities excluded from computation of earnings per share

MSUs, performance shares, RSUs, and stock options and deferred shares associated with our deferred compensation program for non-employee directors that were not included in the computation of diluted earnings per share for those periods because their inclusion would be anti-dilutive were as follows:

	Three months ended June 30,		Six months ended June 30,
(millions)	2017	2016	2017	2016
MSUs, performance shares, RSUs and stock options	0.7	1.7	0.9	1.7
Deferred shares associated with a deferred compensation program for non-employee directors	—	0.2	—	0.2