Significant Accounting Policies (Details) (USD $)	Mar. 31, 2013	Dec. 31, 2012
Accounts Receivable Purchase Agreement
Maximum amount of accounts receivable to be sold under a Receivables Purchase Agreement ("RPA")	$ 125,000,000
Percentage rate added to floating market rate to get discount margin	2.00%
Accounts receivable sold	70,800,000
Retained beneficial interest recorded	4,800,000
Goodwill
Goodwill	468,456,000	470,506,000
2012 Acquisitions \| Land segment \| Adjustment
Goodwill
Goodwill	(2,000,000)
Reclassification to identifiable intangible assets	3,300,000
Increase (decrease) in acquired net assets	(900,000)
Increase in assumed liabilities	400,000
2012 Acquisitions \| Land segment \| Reclass
Goodwill
Goodwill	(6,500,000)
2012 Acquisitions \| Aviation segment \| Reclass
Goodwill
Goodwill	$ 6,500,000

Represents the percentage rate added to floating market rate to get discount margin.

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- Definition

Amount of acquisition cost of a business combination allocated to assets, excluding financial assets and goodwill, lacking physical substance.

+ References

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The amount of acquisition cost of a business combination allocated to liabilities assumed.

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-Publisher FASB

-Name Emerging Issues Task Force (EITF)

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The amount of acquisition cost of a business combination allocated to net tangible assets.

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Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

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- Definition

This includes the recognized portion of the total principal amount of financial assets which have been either securitized, used in an asset-backed financing arrangement, or similar transfer which are accounted for as sales and in which the transferor has continuing involvement with the assets underlying the transaction (including, but not limited to, servicing, recourse, and restrictions on transferor's interests in transferred financial assets).

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- Definition

The face amount of all receivables that will be sold to other entities, including trade and loan receivables.

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