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Cash, Cash Equivalents and Marketable Securities (Notes) | 3 Months Ended
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Mar. 31, 2022
Cash, Cash Equivalents and Marketable Securities [Abstract] |
Cash, Cash Equivalents and Marketable Securities |
3. | Cash, Cash Equivalents and Marketable Securities
The following table summarizes our cash and investments in cash equivalents and marketable securities held by investment managers and overnight investments:
| March 31, 2022 |  | December 31, 2021
(in thousands) | Cash & Cash Equivalents | Marketable Securities | Total |  | Cash & Cash Equivalents | Marketable Securities | Total
Overnight holdings | $ | 566,030 |  | $ | — |  | $ | 566,030 |  |  | $ | 490,154 |  | $ | — |  | $ | 490,154 |
Investment holdings | 13,066 |  | 32,610 |  | 45,676 |  |  | 88,951 |  | 31,791 |  | 120,742 |
Cash in demand accounts | 26,736 |  | — |  | 26,736 |  |  | 47,331 |  | — |  | 47,331 |
Outstanding checks | (29,178) |  | — |  | (29,178) |  |  | (50,624) |  | — |  | (50,624) |
Total | $ | 576,654 |  | $ | 32,610 |  | $ | 609,264 |  |  | $ | 575,812 |  | $ | 31,791 |  | $ | 607,603 |
Our cash and overnight holdings fluctuate based on the timing of clients’ payroll processing cycles. Our cash, cash equivalents and marketable securities at March 31, 2022 and December 31, 2021 included $338.3 million and $424.8 million, respectively, of funds associated with federal and state income tax withholdings, employment taxes, and other payroll deductions, as well as $117.8 million and $20.1 million, respectively, in client prepayments.

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- Definition The entire disclosure of cash, cash equivalents, and debt and equity securities, including any unrealized or realized gain (loss). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -URI http://asc.fasb.org/topic&trid=2196928 + Details
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