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Subsequent Events (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2012 | Feb. 10, 2012 | Dec. 31, 2011 | Sep. 30, 2001
Subsequent Event |  |  |  |
Long-term Purchase Commitment, Amount | $ 21.0 |  |  |
Share repurchase authorization increase |  | 2.8 |  |
Stock Repurchase Shares Authorized |  | 5.0 | 2.2 | 15.4

X
- Definition Share repurchase authorization increase + References No definition available. + Details
Name: | htld_ShareRepurchaseAuthorizationIncrease
Namespace Prefix: | htld_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition The number of shares authorized by an entity's Board of Directors under a stock repurchase plan. + References No definition available. + Details
Name: | htld_StockRepurchaseShares
Namespace Prefix: | htld_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition The minimum amount the entity agreed to spend under the long-term purchase commitment. + References No definition available. + Details
Name: | us-gaap_LongTermPurchaseCommitmentAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_SubsequentEventLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration