9. Equity

Common Stock and Share Repurchase Plan

On October 20, 2015, our Board of Directors increased the number of shares authorized to be repurchased under our share repurchase plan by 7.5 million shares and extended the duration of the plan through December 31, 2018. We repurchase shares through open market purchases under plans complying with Rule 10b5-1 under the Securities Exchange Act of 1934, as amended (the “Exchange Act”). Since initiating the share repurchase plan in 1994, we have repurchased approximately 23.1 million shares at an average cost of $32.94 per share. As of March 31, 2018, we had authorization under the plan to purchase approximately 7.5 million shares, or about 10% of our current outstanding shares. Repurchased and subsequently retired shares are restored to the status of authorized but unissued shares.

Common stock and additional paid-in capital activity included the following:


	Three Months Ended
	March 31, 2018
				Weighted Average
	Shares	Amount		Exercise Price
	(in millions, except share and per share amounts)
Stock-based compensation(1)	269,433	$	1.0
Stock options exercised	48,275		2.8	$	57.91
Share repurchases(2)	(592,564)		(50.0)
Total	(274,856)	$	(46.2)

⁽¹⁾

Stock-based compensation expense of $6.4 million reduced by $5.4 million of payments we made to tax authorities on our employees’ behalf for shares withheld related to net share settlements.

⁽²⁾

Includes 8,120 shares for $0.7 million pending settlement at March 31, 2018.

Dividends

On April 25, 2018, our Board of Directors declared the 2018 second quarter cash dividend of $0.50 per share. The dividend is payable on June 15, 2018 to stockholders of record as of May 25, 2018.

During the first quarters of 2018 and 2017, we declared and paid quarterly dividends of $0.50 and $0.45 per share, or $36.5 million and $32.8 million in total, respectively. During the first quarters of 2018 and 2017, we paid $2.0 million and $0.9 million in dividend equivalents with respect to vested restricted stock units (“RSUs”), respectively.

Stock-Based Compensation

We make annual grants of long-term incentive awards to officers and key employees in the forms of service-based and performance-based RSUs that generally have 3-year vesting periods. The performance-based RSU awards are subject to both service and performance goal criteria. We also make annual grants of stock to the non-employee members of the Board of Directors that include dividend rights and vest immediately upon grant. The fair value of the RSUs and stock grants is determined based on the closing stock price of our common stock on the grant date.

A summary of the status of our unvested service-based and performance-based RSUs as of March 31, 2018 and changes during the quarter then ended is as follows:


		Weighted
		Average Grant
Unvested Shares	Shares	Date Fair Value
Unvested at January 1, 2018	924,575	$	74.09
Granted(1)	474,715		84.26
Vested	(3,032)		71.59
Cancelled or forfeited	(10,018)		73.84
Unvested at March 31, 2018	1,386,240	$	77.58
Shares reserved for future grants (all plans)	1,379,291

⁽¹⁾

474,715 RSUs, including 178,970 performance-based RSUs, were granted in March 2018.

Accumulated Other Comprehensive Loss

Accumulated other comprehensive loss included the following:


			Pension and		Accumulated
	Foreign Currency		Postretirement		Other
	Translation		Benefit Adjustments,		Comprehensive
	Loss		Net of Tax		Loss
	(in millions)
Balance as of January 1, 2018	$	(51.1)	$	(20.5)	$	(71.6)
Current-period change		(2.9)		—		(2.9)
Balance as of March 31, 2018	$	(54.0)	$	(20.5)	$	(74.5)

Foreign currency translation adjustments have not been adjusted for income taxes. Pension and postretirement benefit adjustments are net of taxes of $13.6 million as of March 31, 2018 and December 31, 2017.