XML 60 R42.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Equity-Based Compensation (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2017
Share-based Compensation [Abstract] |
Summary of Compensation Expense Connection with Awards | The Company recognized the following compensation expense in connection with awards that vested under the Plan, the Prior Plan, and the Non-Employee Directors Plan along with the related tax benefits recognized during the years ended December 31 (in thousands):
| 2017 |  | 2016 |  | 2015
Expense recognized under the Prior Plan | $ | 1,059 |  |  | $ | 1,937 |  |  | $ | 1,953 |
Expense recognized under the Plan | 5,643 |  |  | 3,993 |  |  | 1,938 |
Expense recognized under the Non-Employee Directors Plan | 420 |  |  | 443 |  |  | — |
Total stock compensation expense | $ | 7,122 |  |  | $ | 6,373 |  |  | $ | 3,891 |
Tax benefits recognized related to stock compensation expense | $ | 2,133 |  |  | $ | 2,485 |  |  | $ | 1,518 |
Schedule of Number of Awards and Weighted Average Grant Date Fair Value | The following table provides the number of stock unit awards granted and restricted shares issued during the years ended December 31, along with the weighted-average grant-date fair value of each award:
| 2017 |  | 2016 |  | 2015
Awards | Number of Awards |  | Weighted Average Grant Date Fair Value |  | Number of Awards |  | Weighted Average Grant Date Fair Value |  | Number of Awards |  | Weighted Average Grant Date Fair Value
Options | 25,000 |  |  | $ | 12.85 |  |  | — |  |  | $ | — |  |  | 37,500 |  |  | $ | 7.67 |
Deferred stock units | 10,170 |  |  | $ | 34.42 |  |  | 11,945 |  |  | $ | 29.30 |  |  | — |  |  | $ | — |
Restricted shares | 2,034 |  |  | $ | 34.42 |  |  | 3,185 |  |  | $ | 29.30 |  |  | 21,318 |  |  | $ | 17.48 |
Restricted stock units | 133,548 |  |  | $ | 36.56 |  |  | 141,982 |  |  | $ | 25.44 |  |  | 212,419 |  |  | $ | 17.78 |
Performance stock units | 108,748 |  |  | $ | 42.72 |  |  | — |  |  | $ | — |  |  | 396,714 |  |  | $ | 19.78 |
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions | The following table provides the weighted average assumptions used to value stock options issued during the year ended December 31:
Year of Grant |  | Fair Value |  | Expected Life (in years) |  | Expected Stock Volatility |  | Risk-free Interest Rate |  | Expected Dividend Yield
2017 |  | $ | 12.85 |  |  | 4.00 |  | 35.7 | % |  | 1.7 | % |  | — | %
2015 |  | $ | 7.67 |  |  | 4.00 |  | 35.7 | % |  | 1.5 | % |  | — | %
Summary of Ranges of Outstanding and Exercisable Options | The following table summarizes the ranges of outstanding and exercisable options at December 31, 2017:
Range of Exercise Prices | Options Outstanding |  | Weighted Average Remaining Contractual Life (in years) |  | Weighted Average Exercise Price |  | Options Exercisable |  | Weighted Average Exercise Price
$8.90 – $9.32 | 28,750 |  |  | 2.70 |  | $ | 8.90 |  |  | 28,750 |  |  | $ | 8.90 |
$9.33 – $11.73 | 92,441 |  |  | 3.70 |  | $ | 9.74 |  |  | 92,441 |  |  | $ | 9.74 |
$11.74 – $17.94 | 39,475 |  |  | 1.70 |  | $ | 13.72 |  |  | 39,475 |  |  | $ | 13.72 |
$17.95 – $23.80 | 37,000 |  |  | 0.69 |  | $ | 22.16 |  |  | 37,000 |  |  | $ | 22.16 |
$23.81 – $43.05 | 50,000 |  |  | 8.57 |  | $ | 33.90 |  |  | — |  |  | $ | — |
| 247,666 |  |  |  |  |  |  | 197,666 |  |  |
Summary of Stock Options Transactions | The following table summarizes information about stock option transactions:
| Options |  | Weighted Average Exercise Price |  | Weighted Average Remaining Contractual Life (in years) |  | Aggregate Intrinsic Value
Balance at January 1, 2015 | 569,319 |  |  | $ | 15.88 |  |  |  |  |
Granted | 37,500 |  |  | 25.44 |  |  |  |  |
Exercised | (119,096 | ) |  | 15.13 |  |  |  |  |
Expired / Forfeited | (29,374 | ) |  | 20.28 |  |  |  |  |
Balance at December 31, 2015 | 458,349 |  |  | $ | 16.57 |  |  |  |  |
Exercised | (175,125 | ) |  | 19.08 |  |  |  |  |
Forfeited | (6,000 | ) |  | 18.22 |  |  |  |  |
Balance at December 31, 2016 | 277,224 |  |  | $ | 14.95 |  |  |  |  |
Granted | 25,000 |  |  | 42.35 |  |  |  |  |
Exercised | (42,058 | ) |  | 16.02 |  |  |  |  |
Forfeited | (12,500 | ) |  | 25.44 |  |  |  |  |
Balance at December 31, 2017 | 247,666 |  |  | $ | 17.01 |  |  | 5.27 |  | $ | 4,194,000 |
Summary of Information About Restricted Stock Units and Weighted Average Grant Date Fair Value | The following table summarizes information about non-vested restricted stock units, performance stock units (that will convert to shares upon vesting) and restricted shares:
| Restricted Stock Units |  | Weighted Average Grant Date Fair Value |  | Restricted Shares |  | Weighted Average Grant Date Fair Value |  | Performance Stock Units (2) (3) |  | Weighted Average Grant Date Fair Value |  | Deferred Stock Units (1) |  | Weighted Average Grant Date Fair Value
Balance at December 31, 2016 | 536,164 |  |  | $ | 17.79 |  |  | 7,361 |  |  | $ | 17.07 |  |  | 396,714 |  |  | $ | 19.78 |  |  | 11,945 |  |  | $ | 29.30 |
Granted | 133,548 |  |  | 36.56 |  |  | 2,034 |  |  | 34.42 |  |  | 108,748 |  |  | 42.72 |  |  | 10,170 |  |  | 34.42 |
Vested | (202,788 | ) |  | 15.71 |  |  | (5,137 | ) |  | 23.75 |  |  | — |  |  | — |  |  | — |  |  | — |
Forfeited | (25,108 | ) |  | 25.88 |  |  | — |  |  | — |  |  | (25,000 | ) |  | 25.44 |  |  | — |  |  | — |
Balance at December 31, 2017 | 441,816 |  |  | $ | 23.96 |  |  | 4,258 |  |  | $ | 17.30 |  |  | 480,462 |  |  | $ | 24.68 |  |  | 22,115 |  |  | $ | 31.65 |
(1) Vested and issued upon retirement.
Aggregate Intrinsic Value of Options Exercised and Aggregate Fair Value of Restricted Stock Units and Restricted Shares that Vested | The following table sets forth the aggregate intrinsic value of options exercised and aggregate fair value of restricted stock units and restricted shares that vested during the years ended December 31 (in thousands):
| 2017 |  | 2016 |  | 2015
Aggregate intrinsic value of options exercised | $ | 628 |  |  | $ | 2,439 |  |  | $ | 1,089 |
Aggregate fair value of vested restricted stock units | $ | 6,756 |  |  | $ | 4,368 |  |  | $ | 6,578 |
Aggregate fair value of vested restricted shares | $ | 70 |  |  | $ | 247 |  |  | $ | 111 |
Aggregate fair value of vested deferred stock units | $ | 350 |  |  | $ | 443 |  |  | $ | — |
PSUs Eligible for Conversion to Cash | The following table provides the number of PSUs which will convert to cash for the years ending December 31:
| 2016 |  | 2015
Awards | Number of Units (2) |  | Grant Date Fair Value (in $000s) |  | Number of Units (3) |  | Grant Date Fair Value (in $000s)
Performance stock units (1) | 128,000 |  |  | $ | 3,100 |  |  | 219,000 |  |  | $ | 4,039 |
(1) There were no performance stock units that convert to cash granted to participants in 2017. (2) The participants earned 200% of target aggregating 256,000 PSUs earned. This award will convert to cash and be payable in January 2019. (3) The participants earned 200% of target aggregating 438,000 PSUs earned. This award will be converted to cash and will be paid to participants in the first quarter of 2018 at the trailing 90-day closing price of the Company's common stock as of December 31, 2017.
Schedule of Compensation Expense Recognized from Change in Fair Value and Vesting of Performance Stock Units | The following table summarizes the compensation expense recognized from the change in fair value and vesting of performance stock units awarded for the years ended December 31 (in thousands):
| 2017 |  | 2016 |  | 2015
Performance stock unit compensation expense | $ | 3,591 |  |  | $ | 10,377 |  |  | $ | 6,965 |
Cash Paid to Settle Liability Awards | The following table provides the number of restricted stock units credited to active participant accounts, balance of vested and unvested restricted stock units within active participant accounts, payments made with respect to restricted stock units issued under the MSPP, and MSPP expense during years ended December 31:
| 2017 |  | 2016 |  | 2015
Restricted stock units credited | 84,299 |  |  | 198,155 |  |  | 94,047 |
Restricted stock units balance, vested and unvested | 389,189 |  |  | 646,669 |  |  | 519,668 |
Share-based liabilities paid, in thousands | $ | 6,058 |  |  | $ | 3,137 |  |  | $ | 1,901 |
MSPP expense, in thousands | $ | 2,432 |  |  | $ | 8,565 |  |  | $ | 2,767 |

X
- Definition Cash Paid To Settle Liability Awards [Table Text Block] + References No definition available. + Details
Name: | rock_CashPaidToSettleLiabilityAwardsTableTextBlock
Namespace Prefix: | rock_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Schedule of compensation expense recognized from change in fair value and vesting of performance stock units [Table text block]. + References No definition available. + Details
Name: | rock_ScheduleOfCompensationExpenseRecognizedFromChangeInFairValueAndVestingOfPerformanceStockUnitsTableTextBlock
Namespace Prefix: | rock_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of the intrinsic value of options exercised and fair value of restricted stock and restricted stock units vested during the period. + References No definition available. + Details
Name: | rock_ScheduleOfFairValueOfOptionsExercisedAndOtherAwardsVestedTableTextBlock
Namespace Prefix: | rock_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of components of a stock option or other award plan under which equity-based compensation is awarded to employees, typically comprised of the amount of unearned compensation (deferred compensation cost), compensation expense, and changes in the quantity and fair value of the shares (or other type of equity) granted, exercised, forfeited, and issued and outstanding pertaining to that plan. Disclosure may also include nature and general terms of such arrangements that existed during the period and potential effects of those arrangements on shareholders, effect of compensation cost arising from equity-based payment arrangements on the income statement, method of estimating the fair value of the goods or services received, or the fair value of the equity instruments granted, during the period, cash flow effects resulting from equity-based payment arrangements and, for registrants that accelerate vesting of out of the money share options, reasons for the decision to accelerate. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5047-113901 + Details
Name: | us-gaap_DisclosureOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure for stock option plans. Includes, but is not limited to, outstanding awards at beginning and end of year, grants, exercises, forfeitures, and weighted-average grant date fair value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Disclosure of the number and weighted-average grant date fair value for restricted stock and restricted stock units that were outstanding at the beginning and end of the year, and the number of restricted stock and restricted stock units that were granted, vested, or forfeited during the year. + References No definition available. + Details
Name: | us-gaap_ScheduleOfSharebasedCompensationRestrictedStockAndRestrictedStockUnitsActivityTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_ShareBasedCompensationAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the weighted-average grant-date fair value of equity options or other equity instruments granted during the year. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValueTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of number, weighted-average exercise price or conversion ratio, aggregate intrinsic value, and weighted-average remaining contractual term for outstanding and exercisable options that are fully vested and expected to vest. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAndExercisableTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the number and weighted-average grant date fair value for outstanding performance shares. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationPerformanceSharesAwardOutstandingActivityTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration