|6 Months Ended
Mar. 31, 2021
|Organization, Consolidation and Presentation of Financial Statements [Abstract]
Under a resolution adopted in March 2020, the Board of Directors authorized the purchase, at management's discretion, of up to $200 million of our common stock. This supplemented a similar resolution adopted in June 2018. During the six months ended March 31, 2021, we purchased approximately 52,000 shares of our common stock at a cost of $3.4 million. During the six months ended March 31, 2020, we purchased approximately 2,767,000 shares of our common stock at a cost of $167.0 million. At March 31, 2021, $146.7 million remained available for future stock repurchases.
During the six months ended March 31, 2021, we granted approximately 315,000 restricted stock units (RSUs) to our employees. Most of these awards will vest ratably over four years, as opposed to five years in previous years. In addition, we awarded approximately 85,000 performance stock units in the six months ended March 31, 2021, to certain executives that will vest at the end of a three-year performance period with the actual number of vested units dependent upon the Company's achievement of certain performance targets.
Our deferred compensation plan uses both mutual fund and life insurance investments to fund its obligations. The mutual funds are recorded at fair value, based upon quoted prices in active markets (Level 1), and the life insurance investments at cash surrender value; changes in value are reported in our consolidated statements of operations. At March 31, 2021, the deferred compensation plan held $27.1 million of the mutual fund investments.
The carrying amounts of cash and cash equivalents, accounts receivable, accounts payable, and other amounts included within current assets and liabilities that meet the definition of a financial instrument are shown at values equivalent to fair value due to the short-term nature of these items. Our debt balances are principally from credit
facilities which can be utilized and repaid as required and whose rates are based upon prevailing market conditions; accordingly, we believe the balance disclosed approximates the fair value. Our accounts receivable billed and billable balance includes both amounts invoiced and amounts that are ready to be invoiced where the funds are collectible within standard invoice terms. Our accounts receivable unbilled balance includes balances where revenue has been earned but no invoice was issued on or before March 31, 2021. Restricted cash represents funds which are held in our bank accounts but which we are precluded from using for general business needs through contractual requirements; these requirements include serving as collateral for lease, credit card, or letter of credit arrangements, or where we hold funds on behalf of clients. Restricted cash is included within "prepaid expenses and other current assets" on our consolidated balance sheets and is included within "cash, cash equivalents, and restricted cash" in our consolidated statements of cash flows. A reconciliation of these balances is shown below.
Supplementary Cash Flow Information