Note 10. Stock‑Based Compensation Plans

We grant stock‑based compensation to our employees and directors. At December 31, 2017, an aggregate of 1,745,716 shares were authorized for future grant under our various stock‑based compensation plans, including stock options, restricted stock units, and restricted stock awards. Awards that expire or are canceled without delivery of shares generally become available for issuance under the plans. As stock options are exercised, restricted stock units and restricted stock awards vest, we issue new shares of Reliance common stock.

Stock Options

Stock option activity under all the plans is as follows:


				Weighted Average
				Remaining	Aggregate
	Option	Weighted Average		Contractual Term	Intrinsic Value
Stock Options	Shares	Exercise Price		(in years)	(in millions)
Outstanding at January 1, 2015	1,327,412	$	49.66
Exercised	(390,606)		48.19
Expired or forfeited	(2,481)		51.96
Outstanding at December 31, 2015	934,325		50.26
Exercised	(753,645)		49.70
Outstanding at December 31, 2016	180,680		52.61
Exercised	(98,405)		52.41
Expired or forfeited	(7,000)		58.68
Outstanding at December 31, 2017	75,275	$	52.30	0.9	$	2.5
Exercisable at December 31, 2017	75,275	$	52.30	0.9	$	2.5

All stock options outstanding at December 31, 2017 had four-year vesting periods and seven-year terms, with the exception of 40,000 options granted to our non‑employee directors that had one-year vesting periods and ten-year terms.

There were no unvested stock options at December 31, 2017 and 2016.

Proceeds from stock options exercised under all stock option plans in 2017, 2016 and 2015 were $5.2 million, $37.5 million and $15.1 million, respectively. The total intrinsic values of all options exercised in 2017, 2016 and 2015 were $2.8 million, $16.3 million and $4.8 million, respectively.

The tax benefit realized from option exercises in 2017, 2016 and 2015 were $8.4 million, $14.3 million and $7.6 million, respectively.

The following tabulation summarizes certain information concerning outstanding and exercisable options as of December 31, 2017:


		Options Outstanding and Exercisable
		Weighted Average
		Remaining	Weighted
Range of	Outstanding at	Contractual Life	Average
Exercise Price	December 31, 2017	in Years	Exercise Price
$38	12,000	1.4	$	38.00
$44 - $45	16,000	2.4		44.99
$55 - $56	35,275	0.1		55.73
$66 - $67	12,000	0.4		66.28
$38 - $67	75,275	0.9	$	52.30

Restricted Stock

In 2017, 2016 and 2015, we granted 446,525, 512,895 and 507,760, respectively, restricted stock units (“RSUs”) to key employees pursuant to the Amended and Restated Stock Option and Restricted Stock Plan. Each RSU consists of the right to receive one share of our common stock and dividend equivalent rights, subject to forfeiture, equal to the accrued cash or stock dividends where the record date for such dividends is after the grant date but before the shares vest. Additionally, each 2017, 2016 and 2015 RSU granted has a service-based condition and cliff vests at December 1, 2019, December 31, 2018 and December 31, 2017, respectively, if the recipient is an employee on those dates. In addition to the service-based condition, 169,009, 190,175, and 185,450 of the RSUs granted in 2017, 2016 and 2015, respectively, also have performance goals and vest only upon the satisfaction of the service-based condition and certain three-year performance targets. In addition to the 2015 RSUs described above, we also granted 10,000 service-based and 40,000 performance-based RSUs to our former CEO as a result of his planned retirement in July 2016 that had a service-based condition and eighteen-month performance targets ended June 30, 2016. The fair value of the 2017, 2016 and 2015 RSUs granted was $79.60 per share, $69.16 per share and $59.27 per share, respectively, determined based on the closing price of our common stock on the grant date.

In 2017, 2016 and 2015, 18,120, 11,851, and 12,719 shares of restricted stock, respectively, were granted to the non‑employee members of the Board of Directors pursuant to the Directors Equity Plan. The fair value of the restricted stock granted in 2017, 2016, and 2015, was $71.73 per share, $70.88 per share, and $66.03 per share, respectively, determined based on the closing price of our common stock on the grant date. The awards include dividend rights and vest immediately upon grant.

In 2017, 2016 and 2015, we made payments of $9.3 million, $6.4 million and $4.5 million, respectively, to tax authorities on our employees’ behalf for shares withheld related to net share settlements. These payments are reflected in the Stock-based compensation caption of the statement of equity.

A summary of the status of our unvested service-based and performance-based RSUs as of December 31, 2017 and changes during the year then ended is as follows:



		Weighted
		Average Grant
Unvested Shares	Shares	Date Fair Value
Unvested at January 1, 2017	985,540	$	64.34
Granted	446,525		79.60
Vested	(467,968)		59.33
Canceled or forfeited	(39,522)		67.99
Unvested at December 31, 2017	924,575	$	74.09

Unrecognized Compensation Cost

As of December 31, 2017, there was $39.5 million of total unrecognized compensation cost related to unvested stock‑based compensation awards granted under all stock‑based compensation plans. That cost is expected to be recognized over a weighted average period of 1.33 years.