Compensation Plans (Stock Based Compensation) (Details) - USD ($) $ in Billions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Payment Arrangement [Abstract]
Total stock-based compensation expense	$ 13.4	$ 11.7	$ 10.0
Stock-based compensation expense, awards we expect to settle in Alphabet stock	12.8	10.8	9.4
Tax benefits on total stock-based compensation expense	2.7	1.8	1.5
Tax benefit realized related to awards vested or exercised	$ 3.6	$ 2.2	$ 2.1

Share-based Payment Arrangement, Noncash Expense, Including Liabilities Settled

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- Definition

Reductions in the entity's income taxes that arise when compensation cost (from non-qualified stock options, vesting of restricted stock units and restricted stock) recognized on the entity's tax return exceeds compensation cost from non-qualified stock options, restricted stock units and restricted stock recognized on the income statement. Includes excess tax benefit realized.

+ References

No definition available.

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- Definition

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
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-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
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- References

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Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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