CONDENSED CONSOLIDATED BALANCE SHEETS - UNAUDITED - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 195,365	$ 188,699
Short-term investments	29,175	51,598
Total cash, cash equivalents and short-term investments	224,540	240,297
Settlement and merchant reserve assets	158,925	166,031
Trade accounts receivable:
Billed, net of allowance of $3,157 and $3,628	243,160	226,623
Unbilled	38,099	37,785
Income taxes receivable	3,889	2,167
Other current assets	53,104	41,688
Total current assets	721,717	714,591
Non-current assets:
Property and equipment, net of depreciation of $110,862 and $105,073	76,725	81,759
Operating lease right-of-use assets	96,101	110,756
Intangible assets	83,728	74,465
Goodwill	313,246	272,322
Customer contract costs, net of amortization of $50,700 and $39,893	47,249	47,238
Deferred income taxes	9,156	10,205
Other assets	16,834	20,664
Total non-current assets	643,039	617,409
Total assets	1,364,756	1,332,000
Current liabilities:
Current portion of long-term debt, net of unamortized discounts of $930 and zero	236,570	14,063
Operating lease liabilities	23,609	22,651
Customer deposits	32,232	39,992
Trade accounts payable	32,080	29,834
Accrued employee compensation	93,125	86,289
Settlement and merchant reserve liabilities	157,308	165,064
Deferred revenue	64,252	52,357
Income taxes payable	2,192	6,627
Other current liabilities	21,873	19,383
Total current liabilities	663,241	436,260
Non-current liabilities:
Long-term debt, net of unamortized discounts of $3,595 and $5,346	138,905	337,154
Operating lease liabilities	80,373	95,926
Deferred revenue	14,006	17,275
Income taxes payable	2,445	2,436
Deferred income taxes	6,700	5,109
Other non-current liabilities	15,462	15,445
Total non-current liabilities	257,891	473,345
Total liabilities	921,132	909,605
Stockholders' equity:
Preferred stock, par value $.01 per share; 10,000 shares authorized; zero shares issued and outstanding
Common stock, par value $.01 per share; 100,000 shares authorized; 32,687 and 32,713 shares outstanding	704	700
Additional paid-in capital	482,387	470,557
Treasury stock, at cost; 36,418 and 35,980 shares	(914,274)	(894,126)
Accumulated other comprehensive income (loss):
Unrealized gains on short-term investments, net of tax	3	13
Cumulative foreign currency translation adjustments	(35,786)	(31,151)
Accumulated earnings	906,955	876,402
Total CSG stockholders' equity	439,989	422,395
Noncontrolling interest	3,635
Total stockholders' equity	443,624	422,395
Total liabilities and stockholders' equity	1,364,756	1,332,000
Software
Non-current assets:
Intangible assets	28,696	26,453
Acquired customer contracts
Non-current assets:
Intangible assets	$ 55,032	$ 48,012