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Income Taxes - Components of Aon's deferred tax assets and liabilities (Details) - USD ($) $ in Millions | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Deferred tax assets: |  |
Net operating loss, capital loss, interest, and tax credit carryforwards | $ 440 | $ 563
Employee benefit plans | 373 | 351
Lease liabilities | 247 |
Accrued interest | 116 | 0
Other accrued expenses | 68 | 98
Investment basis differences | 28 | 28
Deferred revenue | 24 | 29
Lease and service guarantees | 3 | 5
Other | 57 | 46
Total | 1,356 | 1,120
Valuation allowance on deferred tax assets | (200) | (171)
Total | 1,156 | 949
Deferred tax liabilities: |  |
Intangibles and property, plant and equipment | (251) | (310)
Lease right-of-use asset | (219) |
Deferred costs | (128) | (143)
Unremitted earnings | (28) | (30)
Unrealized foreign exchange gains | (26) | (26)
Other accrued expenses | (25) | (36)
Other | (33) | (24)
Total | (710) | (569)
Net deferred tax asset | $ 446 | $ 380

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- Definition The sum of the tax effects as of the balance sheet date of the amount of (1) excess of tax deductions over gross income in a year which cannot be used on the tax returns in the current year but can be carried forward to reduce taxable income or income taxes payable in a future year, for which there must be sufficient tax-basis income to utilize a portion or all of the carryforward amount to realize the deferred tax asset, and capital losses that cannot be utilized on the tax return during a period that have been carried forward to reduce taxable income or taxes payable in a future year and (2) future tax deductions arising from all unused tax credit carryforwards which have been reduced by a valuation allowance. + References No definition available. + Details
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