Condensed consolidated interim financial statements Condensed consolidaed interim financial statements (Policies)	6 Months Ended
Jun. 30, 2019
Accounting Policies [Abstract]
Condensed consolidated interim financial statements	The condensed consolidated interim financial statements included in this report are prepared by the Company without audit. In the opinion of management, all adjustments necessary for a fair presentation of the results of operations are reflected in these condensed consolidated interim financial statements. All significant intercompany accounts and transactions have been eliminated. The preparation of these financial statements requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses. The most significant estimates and assumptions underlying these financial statements and accompanying notes generally involve revenue recognition and accounts receivable, leases, impairments of goodwill and investments, accounting for income taxes, consolidation of variable interest entities and certain fair value estimates. The results of operations for the six months ended June 30, 2019 are not necessarily indicative of the operating results for the full year. The condensed consolidated interim financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 (10-K). Prior year balances and amounts have been reclassified to conform to the current year presentation. The Company has evaluated subsequent events through the date these condensed consolidated financial statements were issued and has included all necessary adjustments and disclosures.
Earnings Per Share	Basic earnings per share is calculated by dividing net income attributable to the Company, adjusted for any change in noncontrolling interest redemption rights in excess of fair value, by the weighted average number of common shares outstanding, net of the weighted average shares held in escrow that under certain circumstances may have been returned to the Company. Diluted earnings per share includes the dilutive effect of outstanding stock-settled stock appreciation rights and unvested stock units (under the treasury stock method) as well as the weighted average shares held in escrow that were outstanding during the period.
Short-term and Long-term Investments	Debt securities: The Company's short-term debt investments are principally bank certificates of deposit with contractual maturities longer than three months but shorter than one year. These debt securities are accounted for as held to maturity and recorded at amortized cost, which approximates their fair values at June 30, 2019 and December 31, 2018. Equity securities: The Company's equity investments in mutual funds and common stock are held within a trust to fund existing obligations associated with several of the Company’s non-qualified deferred compensation plans.
Income Taxes	The Company recognizes accrued interest and penalties related to unrecognized tax benefits in its income tax expense.
Long-term debt	The cap agreements are designated as cash flow hedges and, as a result, changes in the fair values of these cap agreements are reported in other comprehensive income. The amortization of the original cap premium is recognized as a component of debt expense on a straight-line basis over the terms of the cap agreements.
Long-term incentive compensation	The Company’s stock-based compensation expense for stock-settled awards is measured at the estimated fair value of awards on the date of grant and recognized on a cumulative straight-line basis over the vesting terms of the awards unless the stock awards are based on non-market based performance metrics, in which case expense is adjusted for expected ultimate payouts as of the end of each reporting period. Stock-based compensation expense for cash-settled awards is based on their estimated fair values as of the end of each reporting period. The expense for all stock-based awards is recognized net of expected forfeitures.
Comprehensive Income	Prior to January 1, 2018, unrealized gains and losses on available-for-sale equity securities were recorded to accumulated other comprehensive income and reclassified to other income when realized. From January 1, 2018, unrealized gains and losses on investment securities are recorded directly to other income rather than to accumulated other comprehensive income.
Variable Interest Entities	The Company relies on the operating activities of certain legal entities that it does not directly own or control, but over which it has indirect influence and of which it is considered the primary beneficiary. These entities are subject to the consolidation guidance applicable to variable interest entities (VIEs). There have been no material changes in the nature of the Company's arrangements with VIEs or its judgments concerning them from those described in Note 23 to the Company's consolidated financial statements included in the 10-K.
Fair Value of Financial Instruments	Investments in equity securities represent investments in various open-ended registered investment companies (mutual funds) and common stock and are recorded at estimated fair value based on reported market prices or redemption prices, as applicable. See Note 5 to these condensed consolidated financial statements for further discussion. Interest rate cap agreements are recorded at fair value estimated from valuation models utilizing the income approach and commonly accepted valuation techniques that use inputs from closing prices for similar assets and liabilities in active markets as well as other relevant observable market inputs at quoted intervals such as current interest rates, forward yield curves, implied volatility and credit default swap pricing. See Note 9 to these condensed consolidated financial statements for further discussion. The estimated fair value measurements of contingent earn-out obligations are primarily based on unobservable inputs, including projected EBITDA.
New Accounting Standards	In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). The amendments in Topic 842 revise the accounting related to lessee accounting. Under the new guidance, lessees are required to recognize a lease liability and a right-of-use asset for substantially all leases with lease terms in excess of twelve months. The new lease guidance also simplifies the accounting for sale and leaseback transactions primarily because lessees must recognize lease assets and lease liabilities. The Company adopted Topic 842 beginning on January 1, 2019 through a modified retrospective approach for leases existing at the adoption date with a cumulative effect adjustment. The Company elected to apply the package of practical expedients to not recast prior conclusions related to contracts containing leases, lease classification and initial direct costs. Adoption of the new standard resulted in the recording of operating right-of-use assets of $2,783,784, operating lease liabilities of $3,001,354 and an adjustment to retained earnings of $39,876, primarily related to deferred gains on prior sale leaseback transactions as of January 1, 2019. The standard did not materially impact the Company's consolidated net earnings and had no impact on cash flows. See Note 10 to these condensed consolidated financial statements for further details. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The amendments in this ASU change the approach for recognizing credit losses on financial assets from the incurred loss methodology in current GAAP to a methodology that reflects current expected credit losses, which requires consideration of a broader range of reasonable and supportable information to inform those credit loss estimates. The current incurred loss model delays recognition of credit losses until it is probable that a loss has been incurred, while this ASU’s new current expected credit loss model requires estimation of credit losses expected over the life of the financial asset or group of similar financial assets. The amendments in this ASU are effective for the Company on January 1, 2020 and are to be applied on a modified-retrospective approach. The Company is still evaluating certain aspects of this ASU as well as the impacts it may have on its consolidated financial statements when adopted on January 1, 2020. In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities. The amendments in this ASU better align an entity’s risk management activities and financial reporting for hedging relationships through changes to both the designation and measurement guidance for qualifying hedging relationships and the presentation of hedge results. The amendments in this ASU were effective for the Company on January 1, 2019 and are to be applied prospectively. The adoption of this ASU did not have a material impact on the Company’s consolidated financial statements when adopted on January 1, 2019. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework -Changes to the Disclosure Requirements for Fair Value Measurement. The applicable amendments in this ASU remove requirements for disclosures concerning transfers between fair value measurement levels 1, 2 and 3 and disclosures concerning valuation processes for level 3 fair value measurements. The applicable amendments in this ASU also add a requirement to separately disclose the changes in unrealized gains and losses included in other comprehensive income for the reporting period for level 3 items measured at fair value on a recurring basis, and require disclosure of the range and weighted average of significant unobservable inputs used to develop level 3 fair value measurements. The amendments in this ASU are effective for the Company beginning on January 1, 2020 and its new requirements are to be applied on a prospective basis. The adoption of this ASU is not expected to have a material impact on the Company’s consolidated financial statements.

Condensed consolidated interim financial statements Condensed consolidaed interim financial statements (Policies)

6 Months Ended

Jun. 30, 2019

Condensed consolidated interim financial statements

The condensed consolidated interim financial statements included in this report are prepared by the Company without audit. In the opinion of management, all adjustments necessary for a fair presentation of the results of operations are reflected in these condensed consolidated interim financial statements. All significant intercompany accounts and transactions have been eliminated. The preparation of these financial statements requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses. The most significant estimates and assumptions underlying these financial statements and accompanying notes generally involve revenue recognition and accounts receivable, leases, impairments of goodwill and investments, accounting for income taxes, consolidation of variable interest entities and certain fair value estimates. The results of operations for the six months ended June 30, 2019 are not necessarily indicative of the operating results for the full year. The condensed consolidated interim financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 (10-K). Prior year balances and amounts have been reclassified to conform to the current year presentation. The Company has evaluated subsequent events through the date these condensed consolidated financial statements were issued and has included all necessary adjustments and disclosures.

Earnings Per Share

Basic earnings per share is calculated by dividing net income attributable to the Company, adjusted for any change in noncontrolling interest redemption rights in excess of fair value, by the weighted average number of common shares outstanding, net of the weighted average shares held in escrow that under certain circumstances may have been returned to the Company.

Diluted earnings per share includes the dilutive effect of outstanding stock-settled stock appreciation rights and unvested stock units (under the treasury stock method) as well as the weighted average shares held in escrow that were outstanding during the period.

Short-term and Long-term Investments

Debt securities: The Company's short-term debt investments are principally bank certificates of deposit with contractual maturities longer than three months but shorter than one year. These debt securities are accounted for as held to maturity and recorded at amortized cost, which approximates their fair values at June 30, 2019 and December 31, 2018.

Equity securities: The Company's equity investments in mutual funds and common stock are held within a trust to fund existing obligations associated with several of the Company’s non-qualified deferred compensation plans.

Income Taxes

The Company recognizes accrued interest and penalties related to unrecognized tax benefits in its income tax expense.

Long-term debt

The cap agreements are designated as cash flow hedges and, as a result, changes in the fair values of these cap agreements are reported in other comprehensive income. The amortization of the original cap premium is recognized as a component of debt expense on a straight-line basis over the terms of the cap agreements.

Long-term incentive compensation

The Company’s stock-based compensation expense for stock-settled awards is measured at the estimated fair value of awards on the date of grant and recognized on a cumulative straight-line basis over the vesting terms of the awards unless the stock awards are based on non-market based performance metrics, in which case expense is adjusted for expected ultimate payouts as of the end of each reporting period. Stock-based compensation expense for cash-settled awards is based on their estimated fair values as of the end of each reporting period. The expense for all stock-based awards is recognized net of expected forfeitures.

Comprehensive Income

Prior to January 1, 2018, unrealized gains and losses on available-for-sale equity securities were recorded to accumulated other comprehensive income and reclassified to other income when realized. From January 1, 2018, unrealized

gains and losses on investment securities are recorded directly to other income rather than to accumulated other comprehensive income.

Variable Interest Entities

The Company relies on the operating activities of certain legal entities that it does not directly own or control, but over which it has indirect influence and of which it is considered the primary beneficiary. These entities are subject to the consolidation guidance applicable to variable interest entities (VIEs).

There have been no material changes in the nature of the Company's arrangements with VIEs or its judgments concerning them from those described in Note 23 to the Company's consolidated financial statements included in the 10-K.

Fair Value of Financial Instruments

Investments in equity securities represent investments in various open-ended registered investment companies (mutual funds) and common stock and are recorded at estimated fair value based on reported market prices or redemption prices, as applicable. See Note 5 to these condensed consolidated financial statements for further discussion.

Interest rate cap agreements are recorded at fair value estimated from valuation models utilizing the income approach and commonly accepted valuation techniques that use inputs from closing prices for similar assets and liabilities in active markets as well as other relevant observable market inputs at quoted intervals such as current interest rates, forward yield curves, implied volatility and credit default swap pricing. See Note 9 to these condensed consolidated financial statements for further discussion.

The estimated fair value measurements of contingent earn-out obligations are primarily based on unobservable inputs, including projected EBITDA.

New Accounting Standards

In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). The amendments in Topic 842 revise the accounting related to lessee accounting. Under the new guidance, lessees are required to recognize a lease liability and a right-of-use asset for substantially all leases with lease terms in excess of twelve months. The new lease guidance also simplifies the accounting for sale and leaseback transactions primarily because lessees must recognize lease assets and lease liabilities. The Company adopted Topic 842 beginning on January 1, 2019 through a modified retrospective approach for leases existing at the adoption date with a cumulative effect adjustment. The Company elected to apply the package of practical expedients to not recast prior conclusions related to contracts containing leases, lease classification and initial direct costs. Adoption of the new standard

resulted in the recording of operating right-of-use assets of $2,783,784, operating lease liabilities of $3,001,354 and an adjustment to retained earnings of $39,876, primarily related to deferred gains on prior sale leaseback transactions as of January 1, 2019. The standard did not materially impact the Company's consolidated net earnings and had no impact on cash flows. See Note 10 to these condensed consolidated financial statements for further details.

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. The amendments in this ASU change the approach for recognizing credit losses on financial assets from the incurred loss methodology in current GAAP to a methodology that reflects current expected credit losses, which requires consideration of a broader range of reasonable and supportable information to inform those credit loss estimates. The current incurred loss model delays recognition of credit losses until it is probable that a loss has been incurred, while this ASU’s new current expected credit loss model requires estimation of credit losses expected over the life of the financial asset or group of similar financial assets. The amendments in this ASU are effective for the Company on January 1, 2020 and are to be applied on a modified-retrospective approach. The Company is still evaluating certain aspects of this ASU as well as the impacts it may have on its consolidated financial statements when adopted on January 1, 2020.

In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities. The amendments in this ASU better align an entity’s risk management activities and financial reporting for hedging relationships through changes to both the designation and measurement guidance for qualifying hedging relationships and the presentation of hedge results. The amendments in this ASU were effective for the Company on January 1, 2019 and are to be applied prospectively. The adoption of this ASU did not have a material impact on the Company’s consolidated financial statements when adopted on January 1, 2019.

In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework -Changes to the Disclosure Requirements for Fair Value Measurement. The applicable amendments in this ASU remove requirements for disclosures concerning transfers between fair value measurement levels 1, 2 and 3 and disclosures concerning valuation processes for level 3 fair value measurements. The applicable amendments in this ASU also add a requirement to separately disclose the changes in unrealized gains and losses included in other comprehensive income for the reporting period for level 3 items measured at fair value on a recurring basis, and require disclosure of the range and weighted average of significant unobservable inputs used to develop level 3 fair value measurements. The amendments in this ASU are effective for the Company beginning on January 1, 2020 and its new requirements are to be applied on a prospective basis. The adoption of this ASU is not expected to have a material impact on the Company’s consolidated financial statements.