CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 339,009	$ 277,766
Accounts receivable and unbilled, net (includes $6.1 million and $2.6 million with related parties at June 30, 2021 and December 31, 2020, respectively)	161,489	160,962
Prepaid expenses and other current assets	49,602	34,923
Total current assets	550,100	473,651
Property and equipment, net	86,195	85,017
Operating lease right-of-use assets	110,730	113,809
Goodwill	662,396	662,396
Intangible assets, net	43,917	46,474
Deferred income taxes	540	536
Other assets	15,830	8,794
Total assets	1,469,708	1,390,677
Current liabilities:
Accounts payable (includes $0.7 million and $0.2 million with related parties at June 30, 2021 and December 31, 2020, respectively)	23,326	26,552
Accrued expenses	145,847	134,367
Advanced billings (includes $5.9 million and $6.5 million with related parties at June 30, 2021 and December 31, 2020, respectively)	282,217	255,664
Other current liabilities	21,217	23,527
Total current liabilities	472,607	440,110
Operating lease liabilities	112,850	115,143
Deferred income tax liability	16,242	13,551
Other long-term liabilities	16,127	16,094
Total liabilities	617,826	584,898
Commitments and contingencies (see Note 11)
Shareholders’ equity:
Preferred stock - $0.01 par-value; 5,000,000 shares authorized; no shares issued and outstanding at June 30, 2021 and December 31, 2020, respectively	0	0
Common stock - $0.01 par-value; 250,000,000 shares authorized at June 30, 2021 and December 31, 2020, respectively; 35,819,012 and 35,519,989 shares issued and outstanding at June 30, 2021 and December 31, 2020, respectively	358	355
Treasury stock - 185,000 shares at June 30, 2021 and December 31, 2020, respectively	(5,578)	(5,578)
Additional paid-in capital	716,547	695,904
Retained earnings	142,315	115,229
Accumulated other comprehensive loss	(1,760)	(131)
Total shareholders’ equity	851,882	805,779
Total liabilities and shareholders’ equity	$ 1,469,708	$ 1,390,677

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

Name:	us-gaap_AccountsPayableCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of obligations incurred and payable, pertaining to costs that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered. Examples include taxes, interest, rent and utilities. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).