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Incentive Plans (Narrative) (Details)		1 Months Ended	3 Months Ended
	Aug. 30, 2013 USD ($) shares	Feb. 29, 2020 $ / shares peerCompanies	Mar. 31, 2021 USD ($) $ / shares	Mar. 31, 2020 USD ($)	Aug. 08, 2013 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation | $			$ 3,600,000	$ 2,800,000
Performance Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units issued, weighted average grant date fair value (in dollars per share)			$ 145.91
2013 Long-Term Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for incentive plan (no more than) (in shares) | shares	5,500,000
Number of shares per employee (no more than) (in shares) | shares	1,000,000
Award expiration period		7 years
2013 Long-Term Incentive Plan | Performance Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum amount payable | $	$ 5,000,000.0
2013 Long-Term Incentive Plan | Nonqualified Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted, fair value (in dollars per share)		$ 32.00
2013 Long-Term Incentive Plan | Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)			3 years
2013 Long-Term Incentive Plan | Return on Average Capital Employed Performance Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)		3 years
Restricted stock units issued, weighted average grant date fair value (in dollars per share)		$ 126.00
2013 Long-Term Incentive Plan | Total Shareholder Return Performance Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)		3 years
Number of companies in total shareholder return peer comparison group | peerCompanies		18
Restricted stock units issued, weighted average grant date fair value (in dollars per share)		$ 168.42
2013 Stock Plan For Non-Employee Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for incentive plan (no more than) (in shares) | shares					500,000
2013 Stock Plan For Non-Employee Directors | Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)			3 years
Restricted stock units issued, weighted average grant date fair value (in dollars per share)			$ 125.04

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