Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 304,658	$ 369,373
Accounts receivable:
Billed receivables	603,832	540,584
Unbilled receivables	482,586	418,288
Allowance for doubtful accounts and unbilled services	(323,658)	(265,500)
Accounts receivable, net	762,760	693,372
Current portion of notes receivable	34,089	35,106
Prepaid expenses and other current assets	74,223	80,810
Total current assets	1,175,730	1,178,661
Property and equipment, net	95,544	93,672
Operating lease assets	153,818	159,777
Goodwill	1,223,764	1,202,767
Other intangible assets, net	43,652	38,432
Notes receivable, net	66,078	69,033
Other assets	35,812	40,800
Total assets	2,794,398	2,783,142
Current liabilities
Accounts payable, accrued expenses and other	164,493	158,936
Accrued compensation	397,147	416,903
Billings in excess of services provided	46,621	36,698
Total current liabilities	608,261	612,537
Long-term debt, net	308,454	275,609
Noncurrent operating lease liabilities	161,976	176,378
Deferred income taxes	150,572	151,352
Other liabilities	90,638	78,124
Total liabilities	1,319,901	1,294,000
Commitments and contingent liabilities (Note 11)
Stockholders' equity
Preferred stock, $0.01 par value; shares authorized — 5,000; none   outstanding	0	0
Common stock, $0.01 par value; shares authorized — 75,000; shares issued and outstanding — 36,028 (2020) and 37,390 (2019)	360	374
Additional paid-in capital	46,642	216,162
Retained earnings	1,568,546	1,413,453
Accumulated other comprehensive loss	(141,051)	(140,847)
Total stockholders' equity	1,474,497	1,489,142
Total liabilities and stockholders' equity	$ 2,794,398	$ 2,783,142