Fair Value Measurements (Fair Value of Financial Assets and Liabilities) (Details 1) - USD ($) $ in Thousands		Mar. 31, 2024	Dec. 31, 2023
Assets
Money Market Investments		$ 7,500	$ 5,600
Marketable equity securities		794,305	690,153
Fair Value, Recurring [Member]
Assets
Money Market Investments	[1]	7,526	5,577
Marketable equity securities	[2]	794,305	690,153
Other current investments	[3]	8,638	6,875
Total Financial Assets		810,469	702,605
Liabilities
Contingent consideration liabilities	[4]	75	788
Interest rate swap	[5]	1,651	2,761
Foreign exchange swap	[6]		86
Mandatorily redeemable noncontrolling interest	[7]	42,549	40,764
Total Financial Liabilities		44,275	44,399
Level 1 | Fair Value, Recurring [Member]
Assets
Money Market Investments	[1]	0	0
Marketable equity securities	[2]	794,305	690,153
Other current investments	[3]	7,682	6,875
Total Financial Assets		801,987	697,028
Liabilities
Contingent consideration liabilities	[4]	0	0
Interest rate swap	[5]	0	0
Foreign exchange swap	[6]		0
Mandatorily redeemable noncontrolling interest	[7]	0	0
Total Financial Liabilities		0	0
Level 2 | Fair Value, Recurring [Member]
Assets
Money Market Investments	[1]	7,526	5,577
Marketable equity securities	[2]	0	0
Other current investments	[3]	956	0
Total Financial Assets		8,482	5,577
Liabilities
Contingent consideration liabilities	[4]	0	0
Interest rate swap	[5]	1,651	2,761
Foreign exchange swap	[6]		86
Mandatorily redeemable noncontrolling interest	[7]	0	0
Total Financial Liabilities		1,651	2,847
Level 3 | Fair Value, Recurring [Member]
Assets
Money Market Investments	[1]	0	0
Marketable equity securities	[2]	0	0
Other current investments	[3]	0	0
Total Financial Assets		0	0
Liabilities
Contingent consideration liabilities	[4]	75	788
Interest rate swap	[5]	0	0
Foreign exchange swap	[6]		0
Mandatorily redeemable noncontrolling interest	[7]	42,549	40,764
Total Financial Liabilities		$ 42,624	$ 41,552

[1] The Company’s money market investments are included in cash and cash equivalents and the value considers the liquidity of the counterparty.

[2] The Company’s investments in marketable equity securities are held in common shares of U.S. corporations that are actively traded on U.S. stock exchanges. Price quotes for these shares are readily available.

[3] Includes U.S. Government Securities, corporate bonds, mutual funds and time deposits. These investments are valued using a market approach based on the quoted market prices of the security or inputs that include quoted market prices for similar instruments and are classified as either Level 1 or Level 2 in the fair value hierarchy.

[4] Included in Accounts payable, vehicle floor plan payable and accrued liabilities and Other Liabilities. The Company determined the fair value of the contingent consideration liabilities using either a Monte Carlo simulation, Black-Scholes model, or probability-weighted analysis depending on the type of target included in the contingent consideration requirements (revenue, EBITDA, client retention). All analyses included estimated financial projections for the acquired businesses and acquisition-specific discount rates.

[5] Included in Other Liabilities. The Company utilized a market approach model using the notional amount of the interest rate swaps multiplied by the observable inputs of time to maturity and market interest rates.

[6] Included in Accounts payable, vehicle floor plan payable and accrued liabilities, and valued based on a valuation model that calculates the differential between the contract price and the market-based forward rate.

[7] The fair value of the mandatorily redeemable noncontrolling interest is based on the fair value of the underlying subsidiaries owned by GHC One and GHC Two, after taking into account any debt and other noncontrolling interests of its subsidiary investments. The fair value of the owned subsidiaries is determined using enterprise value analyses which include an equal weighing between guideline public company and discounted cash flow analyses.