Insperity (NSP) 10-Q 29 Jul 19 2019 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Jul. 22, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2019
Document Transition Report	false
Entity File Number	1-13998
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	76-0479645
Entity Address, Address Line One	19001 Crescent Springs Drive
Entity Address, City or Town	Kingwood,
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77339
City Area Code	281
Local Phone Number	358-8986
Title of 12(b) Security	Common Stock, $.01 par value per share
Entity Trading Symbol	NSP
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		41,186,348
Entity Registrant Name	INSPERITY, INC.
Entity Central Index Key	0001000753
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Amendment Flag	false

CONSOLIDATED BALANCE SHEETS (Un

CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Assets
Cash and cash equivalents	$ 324,926	$ 326,773
Restricted cash	43,268	42,227
Marketable securities	61,129	60,781
Accounts receivable, net	424,135	400,623
Prepaid insurance	24,469	8,411
Other current assets	29,794	27,721
Income taxes receivable	11,456	0
Total current assets	919,177	866,536
Property and equipment, net of accumulated depreciation	120,828	117,213
Right-of-use leased assets	54,189	0
Prepaid health insurance	9,000	9,000
Deposits – health insurance	6,600	6,200
Deposits – workers’ compensation	187,728	166,474
Goodwill and other intangible assets, net	12,720	12,726
Deferred income taxes, net	556	8,816
Other assets	6,197	4,851
Total assets	1,316,995	1,191,816
Current liabilities:
Accounts payable	6,548	10,622
Accrued Payroll Taxes, Current	244,694	261,166
Accrued worksite employee payroll cost	373,532	329,979
Accrued health insurance costs	20,376	35,153
Accrued workers’ compensation costs	47,122	45,818
Accrued corporate payroll and commissions	37,820	60,704
Other accrued liabilities	39,756	28,890
Total current liabilities	769,848	772,332
Noncurrent liabilities:
Accrued workers’ compensation costs	188,241	187,412
Long-term debt	169,400	144,400
Operating lease liabilities, net of current	54,617	0
Other accrued liabilities, net of current	0	9,996
Total noncurrent liabilities	412,258	341,808
Commitments and contingencies
Stockholders’ equity:
Common stock	555	555
Additional paid-in capital	41,009	36,752
Treasury stock, at cost	(383,830)	(357,569)
Retained earnings	477,155	397,938
Total stockholders’ equity	134,889	77,676
Total liabilities and stockholders’ equity	$ 1,316,995	$ 1,191,816

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Revenues(1)	$ 1,043,316	$ 922,295	$ 2,196,326	$ 1,936,667
Payroll taxes, benefits and workers’ compensation costs	869,581	767,751	1,795,874	1,582,403
Gross profit	173,735	154,544	400,452	354,264
Salaries, wages and payroll taxes	74,696	68,748	158,076	155,934
Stock-based compensation	8,256	5,752	14,296	8,887
Commissions	7,741	6,979	14,693	13,045
Advertising	7,548	6,585	12,579	10,150
General and administrative expenses	29,866	27,419	63,028	57,271
Depreciation and amortization	6,908	5,480	13,599	10,693
Total operating expenses	135,015	120,963	276,271	255,980
Operating income	38,720	33,581	124,181	98,284
Other income (expense):
Interest income	2,802	1,807	6,047	3,263
Interest expense	(1,639)	(1,108)	(3,320)	(2,178)
Income before income tax expense	39,883	34,280	126,908	99,369
Income tax expense	11,327	9,720	22,063	24,818
Net income	28,556	24,560	104,845	74,551
Less distributed and undistributed earnings allocated to participating securities	(309)	(346)	(1,183)	(1,064)
Net income allocated to common shares	$ 28,247	$ 24,214	$ 103,662	$ 73,487
Basic net income per share of common stock (in dollars per share)	$ 0.69	$ 0.59	$ 2.55	$ 1.78
Diluted net income per share of common stock (in dollars per share)	$ 0.69	$ 0.58	$ 2.54	$ 1.77
Revenue Composition [Abstract]
Gross billings	$ 6,377,014	$ 5,550,342	$ 13,248,684	$ 11,473,698
Worksite employee payroll cost	5,333,698	4,628,047	11,052,358	9,537,031
Revenues(1)	$ 1,043,316	$ 922,295	$ 2,196,326	$ 1,936,667

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities
Net income	$ 104,845	$ 74,551
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	13,599	10,693
Stock-based compensation	14,296	8,887
Deferred income taxes	8,260	(255)
Changes in operating assets and liabilities:
Accounts receivable	(23,512)	(17,773)
Prepaid insurance	(16,058)	(6,866)
Other current assets	(2,073)	4,351
Other assets	(2,033)	(1,957)
Accounts payable	(4,074)	(2,324)
Payroll taxes and other payroll deductions payable	(16,472)	(89,815)
Accrued worksite employee payroll expense	43,553	28,194
Accrued health insurance costs	(14,777)	(1,948)
Accrued workers’ compensation costs	2,133	9,926
Accrued corporate payroll, commissions and other accrued liabilities	(22,878)	(15,183)
Income taxes payable/receivable	(12,381)	16,808
Total adjustments	(32,417)	(57,262)
Net cash provided by operating activities	72,428	17,289
Marketable securities:
Purchases	(60,609)	(11,849)
Proceeds from dispositions	5,499	5,439
Proceeds from maturities	55,110	1,125
Property and equipment:
Purchases	(17,207)	(14,025)
Net cash used in investing activities	(17,207)	(19,310)
Cash flows from financing activities:
Purchase of treasury stock	(38,796)	(16,227)
Dividends paid	24,740	16,786
Borrowings under revolving line of credit	25,000	0
Other	3,763	1,110
Net cash used in financing activities	(34,773)	(31,903)
Net increase (decrease) in cash, cash equivalents and restricted cash	20,448	(33,924)
Cash, cash equivalents and restricted cash beginning of period	535,474	549,612
Cash, cash equivalents and restricted cash end of period	555,922	515,688
Supplemental Cash Flow Information [Abstract]
Cash and cash equivalents	324,926	308,711
Restricted cash	43,268	41,827
Deposits workers compensation	187,728	165,150
ROU assets obtained in exchange for lease obligations	$ 11,894	$ 0

CONSOLIDATED STATEMENT OF STOCK

CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]
Balance at Dec. 31, 2017	$ 66,321	$ 555	$ 25,337	$ (256,363)	$ 296,792
Purchase of treasury stock, at cost	(16,227)	0	0	(16,227)	0
Issuance of long-term incentive awards and dividend equivalents	0	0	(5,764)	6,619	(855)
Stock-based compensation expense	8,887	0	7,005	1,882	0
Other	1,110	0	785	325	0
Dividends paid	(16,786)	0	0	0	(16,786)
Unrealized gain on marketable securities, net of tax	4	0	0	0	4
Net income	74,551	0	0	0	74,551
Balance at Jun. 30, 2018	117,860	$ 555	27,363	(263,764)	353,706
Balance (shares) at Dec. 31, 2017		55,489
Balance (shares) at Jun. 30, 2018		55,489
Balance at Mar. 31, 2018	102,832	$ 555	22,648	(257,898)	337,527
Purchase of treasury stock, at cost	(7,662)	0	0	(7,662)	0
Stock-based compensation expense	5,752	0	4,165	1,587	0
Other	759	0	550	209	0
Dividends paid	(8,384)	0	0	0	(8,384)
Unrealized gain on marketable securities, net of tax	3	0	0	0	3
Net income	24,560	0	0	0	24,560
Balance at Jun. 30, 2018	117,860	$ 555	27,363	(263,764)	353,706
Balance (shares) at Mar. 31, 2018		55,489
Balance (shares) at Jun. 30, 2018		55,489
Balance at Dec. 31, 2018	77,676	$ 555	36,752	(357,569)	397,938
Purchase of treasury stock, at cost	(38,796)	0	0	(38,796)	0
Issuance of long-term incentive awards and dividend equivalents	0	0	(7,695)	8,646	(951)
Stock-based compensation expense	14,296	0	10,776	3,520	0
Other	1,545	0	1,176	369	0
Dividends paid	(24,740)	0	0	0	(24,740)
Unrealized gain on marketable securities, net of tax	63	0	0	0	63
Net income	104,845	0	0	0	104,845
Balance at Jun. 30, 2019	134,889	$ 555	41,009	(383,830)	477,155
Balance (shares) at Dec. 31, 2018		55,489
Balance (shares) at Jun. 30, 2019		55,489
Balance at Mar. 31, 2019	119,194	$ 555	33,833	(376,097)	460,903
Purchase of treasury stock, at cost	(9,759)	0	0	(9,759)	0
Stock-based compensation expense	8,256	0	6,436	1,820	0
Other	946	0	740	206	0
Dividends paid	(12,354)	0	0	0	(12,354)
Unrealized gain on marketable securities, net of tax	50	0	0	0	50
Net income	28,556	0	0	0	28,556
Balance at Jun. 30, 2019	$ 134,889	$ 555	$ 41,009	$ (383,830)	$ 477,155
Balance (shares) at Mar. 31, 2019		55,489
Balance (shares) at Jun. 30, 2019		55,489

Basis of Presentation (Notes)

Basis of Presentation (Notes)	6 Months Ended
	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	1. Basis of Presentation Insperity, Inc., a Delaware corporation (“Insperity,” “we,” “our,” and “us”), provides an array of human resources (“HR”) and business solutions designed to help improve business performance. Our most comprehensive HR services offerings are provided through our professional employer organization (“PEO”) services, known as Workforce Optimization ® and Workforce Synchronization TM solutions (together, our “PEO HR Outsourcing solutions”), which encompass a broad range of HR functions, including payroll and employment administration, employee benefits, workers’ compensation, government compliance, performance management, and training and development services, along with our cloud-based human capital management solution, the Insperity Premier TM platform. In addition to our PEO HR Outsourcing solutions, we also offer a comprehensive traditional payroll and human capital management solution, known as Workforce Acceleration. We also offer a number of other business performance solutions, including Time and Attendance, Performance Management, Organizational Planning, Recruiting Services, Employment Screening, Expense Management, Retirement Services and Insurance Services, many of which are offered as a cloud-based software solution and are offered separately or with our other solutions. The Consolidated Financial Statements include the accounts of Insperity and its wholly owned subsidiaries. Intercompany accounts and transactions have been eliminated in consolidation. The preparation of financial statements in conformity with accounting principles generally accepted in the United States (“GAAP”) requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates. The accompanying Consolidated Financial Statements should be read in conjunction with our audited Consolidated Financial Statements at and for the year ended December 31, 2018 . Our Condensed Consolidated Balance Sheet at December 31, 2018 has been derived from the audited financial statements at that date, but does not include all of the information or footnotes required by GAAP for complete financial statements. Our Condensed Consolidated Balance Sheet at June 30, 2019 and our Consolidated Statements of Operations for the three and six month periods ended June 30, 2019 and 2018 , our Consolidated Statements of Cash Flows for the six month periods ended June 30, 2019 and 2018 and our Consolidated Statements of Stockholders’ Equity for the three and six month periods ended June 30, 2019 and 2018 , have been prepared by us without audit. In the opinion of management, all adjustments, consisting only of normal recurring adjustments necessary to present fairly the consolidated financial position, results of operations and cash flows, have been made. Certain prior year amounts have been reclassified to conform to the 2019 presentation. The results of operations for the interim periods are not necessarily indicative of the operating results for a full year or of future operations.

Accounting Policies (Notes)

Accounting Policies (Notes)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Accounting Policies	2. Accounting Policies Health Insurance Costs We provide group health insurance coverage to our WSEEs in our PEO HR Outsourcing solutions through a national network of carriers, including UnitedHealthcare (“United”), UnitedHealthcare of California, Kaiser Permanente, Blue Shield of California, HMSA BlueCross BlueShield of Hawaii, and Tufts, all of which provide fully insured policies or service contracts. The policy with United provides approximately 87% of our health insurance coverage. While the policy with United is a fully-insured plan, as a result of certain contractual terms, we have accounted for this plan since its inception using a partially self-funded insurance accounting model. Accordingly, we record the costs of the United plan, including an estimate of the incurred claims, taxes and administrative fees (collectively the “Plan Costs”) as benefits expense, which is a component of direct costs, in our Consolidated Statements of Operations. The estimated incurred claims are based upon: (1) the level of claims processed during the quarter; (2) estimated completion rates based upon recent claim development patterns under the plan; and (3) the number of participants in the plan, including both active and COBRA enrollees. Each reporting period, changes in the estimated ultimate costs resulting from claim trends, plan design and migration, participant demographics and other factors are incorporated into the benefits costs. Additionally, since the plan’s inception, under the terms of the contract, United establishes cash funding rates 90 days in advance of the beginning of a reporting quarter. If the Plan Costs for a reporting quarter are greater than the premiums paid and owed to United, a deficit in the plan would be incurred and a liability for the excess costs would be accrued in our Condensed Consolidated Balance Sheets. On the other hand, if the Plan Costs for the reporting quarter are less than the premiums paid and owed to United, a surplus in the plan would be incurred and we would record an asset for the excess premiums in our Condensed Consolidated Balance Sheets. The terms of the arrangement require us to maintain an accumulated cash surplus in the plan of $9.0 million , which is reported as long-term prepaid insurance. In addition, United requires a deposit equal to approximately one day of claims funding activity, which was $5.0 million as of June 30, 2019 , and is reported as a long-term asset. As of June 30, 2019 , Plan Costs were less than the net premiums paid and owed to United by $16.4 million . As this amount is in excess of the agreed-upon $9.0 million surplus maintenance level, the $7.4 million difference is included in prepaid insurance, a current asset , in our Condensed Consolidated Balance Sheets. The premiums, including the additional quarterly premiums, owed to United at June 30, 2019 were $15.0 million , which is included in accrued health insurance costs, a current liability in our Condensed Consolidated Balance Sheets. Our benefits costs incurred in the first six months of 2019 included a charge of $3.5 million for changes in estimated run-off related to prior periods. Workers’ Compensation Costs Our workers’ compensation coverage for our WSEEs in our PEO HR Outsourcing solutions has been provided through an arrangement with the Chubb Group of Insurance Companies or its predecessors (the “Chubb Program”) since 2007. The Chubb Program is fully insured in that Chubb has the responsibility to pay all claims incurred under the policy regardless of whether we satisfy our responsibilities. Under the Chubb Program, we have financial responsibility to Chubb for the first $1 million layer of claims per occurrence and, for claims over $1 million , up to a maximum aggregate amount of $6 million per policy year for claims that exceed $1 million . Chubb bears the financial responsibility for all claims in excess of these levels. Because we bear the financial responsibility for claims up to the levels noted above, such claims, which are the primary component of our workers’ compensation costs, are recorded in the period incurred. Workers’ compensation insurance includes ongoing health care and indemnity coverage whereby claims are paid over numerous years following the date of injury. Accordingly, the accrual of related incurred costs in each reporting period includes estimates, which take into account the ongoing development of claims and therefore requires a significant level of judgment. We utilize a third-party actuary to estimate our loss development rate, which is primarily based upon the nature of WSEEs job responsibilities, the location of WSEEs, the historical frequency and severity of workers’ compensation claims, and an estimate of future cost trends. Each reporting period, changes in the actuarial assumptions resulting from changes in actual claims experience and other trends are incorporated into our workers’ compensation claims cost estimates. During the six months ended June 30, 2019 and 2018 , we reduced accrued workers’ compensation costs by $19.0 million and $10.9 million , respectively, for changes in estimated losses related to prior reporting periods. Workers’ compensation cost estimates are discounted to present value at a rate based upon the U.S. Treasury rates that correspond with the weighted average estimated claim payout period (the average discount rate utilized in the 2019 period was 2.3% and in the 2018 period was 2.5% ) and are accreted over the estimated claim payment period and included as a component of direct costs in our Consolidated Statements of Operations. The following table provides the activity and balances related to incurred but not paid workers’ compensation claims: Six Months Ended June 30, (in thousands) 2019 2018 Beginning balance, January 1, $ 229,639 $ 207,630 Accrued claims 27,299 33,260 Present value discount (2,703 ) (3,360 ) Paid claims (22,727 ) (21,686 ) Ending balance $ 231,508 $ 215,844 Current portion of accrued claims $ 43,267 $ 41,827 Long-term portion of accrued claims 188,241 174,017 Total accrued claims $ 231,508 $ 215,844 The current portion of accrued workers’ compensation costs on our Condensed Consolidated Balance Sheets at June 30, 2019 includes $3.9 million of workers’ compensation administrative fees. As of June 30, 2019 and 2018 , the undiscounted accrued workers’ compensation costs were $250.9 million and $230.4 million , respectively. At the beginning of each policy period, the workers’ compensation insurance carrier establishes monthly funding requirements comprised of premium costs and funds to be set aside for payment of future claims (“claim funds”). The level of claim funds is primarily based upon anticipated WSEE payroll levels and expected workers’ compensation loss rates, as determined by the insurance carrier. Monies funded into the program for incurred claims expected to be paid within one year are recorded as restricted cash, a short-term asset, while the remainder of claim funds are included in deposits – workers’ compensation, a long-term asset in our Condensed Consolidated Balance Sheets. During the six months ended June 30, 2019 , we funded a collateral deposit of $6.4 million for policy years prior to 2007, which increased deposits. As of June 30, 2019 , we had restricted cash of $43.3 million and deposits – workers’ compensation of $187.7 million . Our estimate of incurred claim costs expected to be paid within one year is included in short-term liabilities, while our estimate of incurred claim costs expected to be paid beyond one year is included in long-term liabilities on our Condensed Consolidated Balance Sheets. Revenue and Direct Cost Recognition We enter into contracts with our customers for human resources services based on a stated rate and price in the contract. Our contracts generally have a term of 12 months, but are cancellable at any time by either party with 30-days’ notice. Our performance obligations are satisfied as services are rendered each month. The term between invoicing and when our performance obligations are satisfied is not significant. Payment terms are typically due concurrently with the invoicing of our PEO services. We do not have significant financing components or significant payment terms. Our revenue is generally recognized ratably over the payroll period as WSEEs perform their service at the client worksite. Customers are invoiced concurrently with each periodic payroll of its WSEEs. Revenues that have been recognized but unbilled of $414.6 million and $385.6 million at June 30, 2019 and December 31, 2018 , respectively, are included in accounts receivable, net on our Condensed Consolidated Balance Sheets. Pursuant to the “practical expedients” provided under Accounting Standards Update (“ASU”) No 2014-09, we expense sales commissions when incurred because the terms of our contracts are cancellable by either party with a 30-day notice. These costs are recorded in commissions in our Consolidated Statements of Operations. Our revenue for our PEO HR Outsourcing solutions by geographic region and for our other products and services offerings are as follows: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2019 2018 % Change 2019 2018 % Change Northeast $ 270,475 $ 239,278 13.0 % $ 581,422 $ 511,642 13.6 % Southeast 120,148 108,264 11.0 % 250,054 223,452 11.9 % Central 179,443 153,025 17.3 % 375,196 321,092 16.8 % Southwest 244,462 213,920 14.3 % 514,294 446,785 15.1 % West 215,639 194,986 10.6 % 448,842 407,605 10.1 % 1,030,167 909,473 13.3 % 2,169,808 1,910,576 13.6 % Other revenue 13,149 12,822 2.6 % 26,518 26,091 1.6 % Total revenue $ 1,043,316 $ 922,295 13.1 % $ 2,196,326 $ 1,936,667 13.4 %

Cash, Cash Equivalents and Mark

Cash, Cash Equivalents and Marketable Securities (Notes)	6 Months Ended
	Jun. 30, 2019
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: June 30, 2019 December 31, 2018 (in thousands) Cash & Cash Equivalents Marketable Securities Total Cash & Cash Equivalents Marketable Securities Total Overnight holdings $ 292,464 $ — $ 292,464 $ 311,158 $ — $ 311,158 Investment holdings 13,515 61,129 74,644 16,711 60,781 77,492 Cash in demand accounts 39,915 — 39,915 33,207 — 33,207 Outstanding checks (20,968 ) — (20,968 ) (34,303 ) — (34,303 ) Total $ 324,926 $ 61,129 $ 386,055 $ 326,773 $ 60,781 $ 387,554 Our cash and overnight holdings fluctuate based on the timing of clients’ payroll processing cycles. Included in the cash, cash equivalents and marketable securities at June 30, 2019 and December 31, 2018 are $218.0 million and $224.5 million , respectively, of funds associated with federal and state income tax withholdings, employment taxes and other payroll deductions, as well as $37.4 million and $34.2 million in client prepayments, respectively.

Fair Value Measurements Fair Va

Fair Value Measurements Fair Value Measurements (Notes)	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value Disclosures [Text Block]	4. Fair Value Measurements We account for our financial assets in accordance with Accounting Standard Codification 820, Fair Value Measurement . This standard defines fair value, establishes a framework for measuring fair value and expands disclosures about fair value measurements. The fair value measurement disclosures are grouped into three levels based on valuation factors: • Level 1 - quoted prices in active markets using identical assets • Level 2 - significant other observable inputs, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other observable inputs • Level 3 - significant unobservable inputs Fair Value of Instruments Measured and Recognized at Fair Value The following table summarizes the levels of fair value measurements of our financial assets: June 30, 2019 December 31, 2018 (in thousands) Total Level 1 Level 2 Total Level 1 Level 2 Money market funds $ 303,908 $ 303,908 $ — $ 325,819 $ 325,819 $ — U.S. Treasury bills 59,775 59,775 — 52,197 52,197 — Municipal bonds 3,425 — 3,425 10,634 — 10,634 Total $ 367,108 $ 363,683 $ 3,425 $ 388,650 $ 378,016 $ 10,634 The municipal bond securities valued as Level 2 are primarily pre-refunded municipal bonds that are secured by escrow funds containing U.S. government securities. Our valuation techniques used to measure fair value for these securities during the period consisted primarily of third-party pricing services that utilized actual market data such as trades of comparable bond issues, broker/dealer quotations for the same or similar investments in active markets and other observable inputs. The following is a summary of our available-for-sale marketable securities: (in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value June 30, 2019 U.S. Treasury bills $ 57,650 $ 54 $ — $ 57,704 Municipal bonds 3,425 — — 3,425 Total $ 61,075 $ 54 $ — $ 61,129 December 31, 2018 U.S. Treasury bills $ 50,150 $ — $ (3 ) $ 50,147 Municipal bonds 10,640 1 (7 ) 10,634 Total $ 60,790 $ 1 $ (10 ) $ 60,781 As of June 30, 2019 , the contractual maturities of our marketable securities were as follows: (in thousands) Amortized Cost Estimated Fair Value Less than one year $ 61,075 $ 61,129 One to five years — — Total $ 61,075 $ 61,129 Fair Value of Other Financial Instruments The carrying amounts of cash, cash equivalents, restricted cash, accounts receivable, deposits and accounts payable approximate their fair values due to the short-term maturities of these instruments. As of June 30, 2019 , the carrying value of borrowings under our revolving credit facility approximates fair value and was classified as Level 2 in the fair value hierarchy. Please read Note 5 , “ Long-Term Debt ,” for additional information.

Long-term Debt (Notes)

Long-term Debt (Notes)	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Revolving Credit Facility	5. Long-Term Debt We have a revolving credit facility (the “Facility”) with borrowing capacity up to $350 million . The Facility may be increased to $400 million based on the terms and subject to the conditions set forth in the agreement relating to the Facility (the “Credit Agreement”). The Facility is available for working capital and general corporate purposes, including acquisitions, stock repurchases and issuances of letters of credit. Our obligations under the Facility are secured by 65% of the stock of our captive insurance subsidiary and are guaranteed by all of our domestic subsidiaries. At June 30, 2019 , our outstanding balance on the Facility was $169.4 million , and we had an outstanding $1.0 million letter of credit issued under the Facility, resulting in an available borrowing capacity of $179.6 million . The Facility matures on February 6, 2023 . Borrowings under the Facility bear interest at an alternate base rate or LIBOR , at our option, plus an applicable margin. Depending on our leverage ratio, the applicable margin varies (1) in the case of LIBOR loans, from 1.50% to 2.25% and (2) in the case of alternate base rate loans, from 0.00% to 0.50% . The alternate base rate is the highest of (1) the prime rate most recently published in The Wall Street Journal, (2) the federal funds rate plus 0.50% and (3) the 30-day LIBOR rate plus 2.00% . We also pay an unused commitment fee on the average daily unused portion of the Facility at a rate of 0.25% . The average interest rate for the period ended June 30, 2019 was 4.00% . Interest expense and unused commitment fees are recorded in other income (expense). The Facility contains both affirmative and negative covenants that we believe are customary for arrangements of this nature. Covenants include, but are not limited to, limitations on our ability to incur additional indebtedness, sell material assets, retire, redeem or otherwise reacquire our capital stock, acquire the capital stock or assets of another business, make investments and pay dividends. In addition, the Credit Agreement requires us to comply with financial covenants limiting our total funded debt, minimum interest coverage ratio and maximum leverage ratio. We were in compliance with all financial covenants under the Credit Agreement at June 30, 2019 .

Leases Leases (Notes)

Leases Leases (Notes)	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Lessee, Operating Leases [Text Block]	6. Leases In February 2016, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2016-02, Leases (Topic 842), which requires lessees to recognize a right-of-use (“ROU”) asset and a lease liability for all leases with terms greater than 12 months and also requires disclosures by lessees and lessors about the amount, timing and uncertainty of cash flows arising from leases. Subsequent to the issuance of Topic 842, the FASB clarified the guidance through several ASUs; hereinafter, the collection of lease guidance is referred to as “ASC 842”. On January 1, 2019 we adopted ASC 842 using the modified retrospective transition method. Results for the reporting period beginning January 1, 2019 are presented under ASC 842, while prior period amounts were not adjusted and continue to be reported in accordance with our historical accounting under ASC 840, Leases. Upon adoption of ASC 842, we increased our total assets and liabilities due to the recording of operating lease ROU assets and operating lease liabilities of approximately $50.8 million and $63.7 million , respectively, as of January 1, 2019. These increases did not have a material impact on our results of operations or cash flows. For all leases that commenced before the effective date of ASC 842, we elected to apply the permitted practical expedients to not reassess the following: (1) whether any expired or existing contracts contain leases; (2) the lease classification for any expired or existing leases; and (3) initial direct costs for any existing leases. We determine if an arrangement is a lease at inception of a contract. ROU assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. As most of our leases do not provide an implicit interest rate, we use our incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The lease terms used to calculate the ROU asset and related lease liability include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. Lease expense for operating leases is recognized on a straight-line basis over the lease term as an operating expense. We have lease agreements which require payments for lease and non-lease components and have elected to account for these as a single lease component related to our other operating facilities. We have operating leases for office space, other operating facilities, vehicles and office equipment. Our fixed operating lease costs for the three and six months ended June 30, 2019 were $3.8 million and $7.6 million , respectively, and are included in general and administrative expenses on our Consolidated Statements of Operations. During the six months ended June 30, 2019 , cash paid for amounts included in the measurement of operating lease liabilities was $8.1 million . The following table presents the lease balances within our Condensed Consolidated Balance Sheets, weighted average lease term and weighted average discount rates related to our operating leases: (dollars in thousands) Classification in Condensed Consolidated Balance Sheets June 30, 2019 Operating lease ROU assets Right-of-use leased assets $ 54,189 Lease liabilities: Current operating lease liabilities Other accrued liabilities $ 14,241 Long-term operating lease liabilities Operating lease liabilities, net of current 54,617 Total operating lease liabilities $ 68,858 Less: Landlord funded tenant improvements $ 10,555 Deferred rent 4,114 Operating lease ROU assets $ 54,189 Weighted average remaining lease term (years) 6 Weighted average discount rate 4.7 % The following presents the maturity of our operating leases liabilities as of June 30, 2019 : (in thousands) Operating Leases Remainder of 2019 $ 8,578 2020 16,035 2021 13,185 2022 11,637 2023 9,286 Thereafter 20,606 Total remaining obligation 79,327 Less imputed interest 10,469 Present value of lease liabilities $ 68,858 As of June 30, 2019 , we have additional operating leases that have not yet commenced of $16.6 million with lease terms ranging from 4 years to 7 years.

Stockholders' Equity (Notes)

Stockholders' Equity (Notes)	6 Months Ended
	Jun. 30, 2019
Stockholders' Equity Note [Abstract]
Stockholders Equity	7. Stockholders' Equity During the first six months of 2019 , we repurchased or withheld an aggregate of 315,369 shares of our common stock, as described below. Repurchase Program Our Board of Directors (the “Board”) has authorized a program to repurchase shares of our outstanding common stock (“Repurchase Program”). The purchases are to be made from time to time in the open market or directly from stockholders at prevailing market prices based on market conditions and other factors. During the six months ended June 30, 2019 , 88,210 shares were repurchased under the Repurchase Program. As of June 30, 2019 , we were authorized to repurchase an additional 1,522,945 shares under the Repurchase Program. Withheld Shares During the six months ended June 30, 2019 , we withheld 227,159 shares to satisfy tax withholding obligations for the vesting of long-term incentive and restricted stock awards. Dividends The Board declared quarterly dividends as follows: (amounts per share) 2019 2018 First quarter $ 0.30 $ 0.20 Second quarter 0.30 0.20 During the six months ended June 30, 2019 and 2018 , we paid dividends totaling $24.7 million and $16.8 million , respectively.

Net Income Per Share (Notes)

Net Income Per Share (Notes)	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Net Income per Share	8. Net Income Per Share We utilize the two-class method to compute net income per share. The two-class method allocates a portion of net income to participating securities, which includes unvested awards of share-based payments with non-forfeitable rights to receive dividends. Net income allocated to unvested share-based payments is excluded from net income allocated to common shares. Any undistributed losses resulting from dividends exceeding net income are not allocated to participating securities. Basic net income per share is computed by dividing net income allocated to common shares by the weighted average number of common shares outstanding during the period. Diluted net income per share is computed by dividing net income allocated to common shares by the weighted average number of common shares outstanding during the period, plus the dilutive effect of outstanding stock options. The following table summarizes the net income allocated to common shares and the basic and diluted shares used in the net income per share computations: Three Months Ended June 30, Six Months Ended (in thousands) 2019 2018 2019 2018 Net income $ 28,556 $ 24,560 $ 104,845 $ 74,551 Less distributed and undistributed earnings allocated to participating securities (309 ) (346 ) (1,183 ) (1,064 ) Net income allocated to common shares $ 28,247 $ 24,214 $ 103,662 $ 73,487 Weighted average common shares outstanding 40,771 41,377 40,640 41,301 Incremental shares from assumed LTIP awards and conversions of common stock options 145 156 140 324 Adjusted weighted average common shares outstanding 40,916 41,533 40,780 41,625

Commitments and Contingencies (

Commitments and Contingencies (Notes)	6 Months Ended
	Jun. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. Commitments and Contingencies Worksite Employee 401(k) Retirement Plan Class Action Litigation In December 2015, a class action lawsuit was filed against us and a third-party who served as the discretionary trustee of the Insperity 401(k) retirement plan that is available to eligible worksite employees (the “Plan”) in the United States District Court for the Northern District of Georgia, Atlanta Division, on behalf of Plan participants. The suit generally alleges the third-party discretionary trustee of the Plan and Insperity breached their fiduciary duties to plan participants by selecting an Insperity subsidiary to serve as the recordkeeper for the Plan, by causing participants in the Plan to pay excessive recordkeeping fees to the Insperity subsidiary, by failing to monitor other fiduciaries, and by making imprudent investment choices. The court certified a class defined as “all participants and beneficiaries of the Insperity 401(k) Plan from December 22, 2009 through September 30, 2017.” The court dismissed the breach of fiduciary duty claims relating to the selection of an Insperity subsidiary to serve as the recordkeeper of the Plan. On March 28, 2019, the court partially granted Insperity’s motion for summary judgment, resulting in the dismissal of the claims concerning allegations of excessive recordkeeping fees. The court has denied plaintiffs’ request for a jury trial and has set a bench trial for March 2, 2020. With respect to plaintiffs’ remaining claims, plaintiffs allege damages up to $128 million against all defendants. We believe we have meritorious defenses, and we intend to vigorously defend this litigation. As a result of uncertainty regarding the outcome of this matter, no provision has been made in the accompanying consolidated financial statements. Other Litigation We are a defendant in various other lawsuits and claims arising in the normal course of business. Management believes it has valid defenses in these cases and is defending them vigorously. While the results of litigation cannot be predicted with certainty, management believes the final outcome of such litigation will not have a material adverse effect on our financial position or results of operations.

Accounting Policies (Policies)

Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Health Insurance Costs	Health Insurance Costs We provide group health insurance coverage to our WSEEs in our PEO HR Outsourcing solutions through a national network of carriers, including UnitedHealthcare (“United”), UnitedHealthcare of California, Kaiser Permanente, Blue Shield of California, HMSA BlueCross BlueShield of Hawaii, and Tufts, all of which provide fully insured policies or service contracts. The policy with United provides approximately 87% of our health insurance coverage. While the policy with United is a fully-insured plan, as a result of certain contractual terms, we have accounted for this plan since its inception using a partially self-funded insurance accounting model. Accordingly, we record the costs of the United plan, including an estimate of the incurred claims, taxes and administrative fees (collectively the “Plan Costs”) as benefits expense, which is a component of direct costs, in our Consolidated Statements of Operations. The estimated incurred claims are based upon: (1) the level of claims processed during the quarter; (2) estimated completion rates based upon recent claim development patterns under the plan; and (3) the number of participants in the plan, including both active and COBRA enrollees. Each reporting period, changes in the estimated ultimate costs resulting from claim trends, plan design and migration, participant demographics and other factors are incorporated into the benefits costs. Additionally, since the plan’s inception, under the terms of the contract, United establishes cash funding rates 90 days in advance of the beginning of a reporting quarter. If the Plan Costs for a reporting quarter are greater than the premiums paid and owed to United, a deficit in the plan would be incurred and a liability for the excess costs would be accrued in our Condensed Consolidated Balance Sheets. On the other hand, if the Plan Costs for the reporting quarter are less than the premiums paid and owed to United, a surplus in the plan would be incurred and we would record an asset for the excess premiums in our Condensed Consolidated Balance Sheets. The terms of the arrangement require us to maintain an accumulated cash surplus in the plan of $9.0 million , which is reported as long-term prepaid insurance. In addition, United requires a deposit equal to approximately one day of claims funding activity, which was $5.0 million as of June 30, 2019 , and is reported as a long-term asset. As of June 30, 2019 , Plan Costs were less than the net premiums paid and owed to United by $16.4 million . As this amount is in excess of the agreed-upon $9.0 million surplus maintenance level, the $7.4 million difference is included in prepaid insurance, a current asset , in our Condensed Consolidated Balance Sheets. The premiums, including the additional quarterly premiums, owed to United at June 30, 2019 were $15.0 million , which is included in accrued health insurance costs, a current liability in our Condensed Consolidated Balance Sheets. Our benefits costs incurred in the first six months of 2019 included a charge of $3.5 million for changes in estimated run-off related to prior periods.
Workers' Compensation Costs	Workers’ Compensation Costs Our workers’ compensation coverage for our WSEEs in our PEO HR Outsourcing solutions has been provided through an arrangement with the Chubb Group of Insurance Companies or its predecessors (the “Chubb Program”) since 2007. The Chubb Program is fully insured in that Chubb has the responsibility to pay all claims incurred under the policy regardless of whether we satisfy our responsibilities. Under the Chubb Program, we have financial responsibility to Chubb for the first $1 million layer of claims per occurrence and, for claims over $1 million , up to a maximum aggregate amount of $6 million per policy year for claims that exceed $1 million . Chubb bears the financial responsibility for all claims in excess of these levels. Because we bear the financial responsibility for claims up to the levels noted above, such claims, which are the primary component of our workers’ compensation costs, are recorded in the period incurred. Workers’ compensation insurance includes ongoing health care and indemnity coverage whereby claims are paid over numerous years following the date of injury. Accordingly, the accrual of related incurred costs in each reporting period includes estimates, which take into account the ongoing development of claims and therefore requires a significant level of judgment. We utilize a third-party actuary to estimate our loss development rate, which is primarily based upon the nature of WSEEs job responsibilities, the location of WSEEs, the historical frequency and severity of workers’ compensation claims, and an estimate of future cost trends. Each reporting period, changes in the actuarial assumptions resulting from changes in actual claims experience and other trends are incorporated into our workers’ compensation claims cost estimates. During the six months ended June 30, 2019 and 2018 , we reduced accrued workers’ compensation costs by $19.0 million and $10.9 million , respectively, for changes in estimated losses related to prior reporting periods. Workers’ compensation cost estimates are discounted to present value at a rate based upon the U.S. Treasury rates that correspond with the weighted average estimated claim payout period (the average discount rate utilized in the 2019 period was 2.3% and in the 2018 period was 2.5% ) and are accreted over the estimated claim payment period and included as a component of direct costs in our Consolidated Statements of Operations. The following table provides the activity and balances related to incurred but not paid workers’ compensation claims: Six Months Ended June 30, (in thousands) 2019 2018 Beginning balance, January 1, $ 229,639 $ 207,630 Accrued claims 27,299 33,260 Present value discount (2,703 ) (3,360 ) Paid claims (22,727 ) (21,686 ) Ending balance $ 231,508 $ 215,844 Current portion of accrued claims $ 43,267 $ 41,827 Long-term portion of accrued claims 188,241 174,017 Total accrued claims $ 231,508 $ 215,844 The current portion of accrued workers’ compensation costs on our Condensed Consolidated Balance Sheets at June 30, 2019 includes $3.9 million of workers’ compensation administrative fees. As of June 30, 2019 and 2018 , the undiscounted accrued workers’ compensation costs were $250.9 million and $230.4 million , respectively. At the beginning of each policy period, the workers’ compensation insurance carrier establishes monthly funding requirements comprised of premium costs and funds to be set aside for payment of future claims (“claim funds”). The level of claim funds is primarily based upon anticipated WSEE payroll levels and expected workers’ compensation loss rates, as determined by the insurance carrier. Monies funded into the program for incurred claims expected to be paid within one year are recorded as restricted cash, a short-term asset, while the remainder of claim funds are included in deposits – workers’ compensation, a long-term asset in our Condensed Consolidated Balance Sheets. During the six months ended June 30, 2019 , we funded a collateral deposit of $6.4 million for policy years prior to 2007, which increased deposits. As of June 30, 2019 , we had restricted cash of $43.3 million and deposits – workers’ compensation of $187.7 million . Our estimate of incurred claim costs expected to be paid within one year is included in short-term liabilities, while our estimate of incurred claim costs expected to be paid beyond one year is included in long-term liabilities on our Condensed Consolidated Balance Sheets.
Revenue Recognition	Revenue and Direct Cost Recognition We enter into contracts with our customers for human resources services based on a stated rate and price in the contract. Our contracts generally have a term of 12 months, but are cancellable at any time by either party with 30-days’ notice. Our performance obligations are satisfied as services are rendered each month. The term between invoicing and when our performance obligations are satisfied is not significant. Payment terms are typically due concurrently with the invoicing of our PEO services. We do not have significant financing components or significant payment terms. Our revenue is generally recognized ratably over the payroll period as WSEEs perform their service at the client worksite. Customers are invoiced concurrently with each periodic payroll of its WSEEs. Revenues that have been recognized but unbilled of $414.6 million and $385.6 million at June 30, 2019 and December 31, 2018 , respectively, are included in accounts receivable, net on our Condensed Consolidated Balance Sheets. Pursuant to the “practical expedients” provided under Accounting Standards Update (“ASU”) No 2014-09, we expense sales commissions when incurred because the terms of our contracts are cancellable by either party with a 30-day notice. These costs are recorded in commissions in our Consolidated Statements of Operations. Our revenue for our PEO HR Outsourcing solutions by geographic region and for our other products and services offerings are as follows: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2019 2018 % Change 2019 2018 % Change Northeast $ 270,475 $ 239,278 13.0 % $ 581,422 $ 511,642 13.6 % Southeast 120,148 108,264 11.0 % 250,054 223,452 11.9 % Central 179,443 153,025 17.3 % 375,196 321,092 16.8 % Southwest 244,462 213,920 14.3 % 514,294 446,785 15.1 % West 215,639 194,986 10.6 % 448,842 407,605 10.1 % 1,030,167 909,473 13.3 % 2,169,808 1,910,576 13.6 % Other revenue 13,149 12,822 2.6 % 26,518 26,091 1.6 % Total revenue $ 1,043,316 $ 922,295 13.1 % $ 2,196,326 $ 1,936,667 13.4 %

Fair Value Measurements Fair Vl

Fair Value Measurements Fair Vlue Measurements (Policies)	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments, Policy [Policy Text Block]	We account for our financial assets in accordance with Accounting Standard Codification 820, Fair Value Measurement . This standard defines fair value, establishes a framework for measuring fair value and expands disclosures about fair value measurements. The fair value measurement disclosures are grouped into three levels based on valuation factors: • Level 1 - quoted prices in active markets using identical assets • Level 2 - significant other observable inputs, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other observable inputs • Level 3 - significant unobservable inputs

Leases Leases (Policies)

Leases Leases (Policies)	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Leases of Lessee Disclosure [Text Block]	In February 2016, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2016-02, Leases (Topic 842), which requires lessees to recognize a right-of-use (“ROU”) asset and a lease liability for all leases with terms greater than 12 months and also requires disclosures by lessees and lessors about the amount, timing and uncertainty of cash flows arising from leases. Subsequent to the issuance of Topic 842, the FASB clarified the guidance through several ASUs; hereinafter, the collection of lease guidance is referred to as “ASC 842”. On January 1, 2019 we adopted ASC 842 using the modified retrospective transition method. Results for the reporting period beginning January 1, 2019 are presented under ASC 842, while prior period amounts were not adjusted and continue to be reported in accordance with our historical accounting under ASC 840, Leases. Upon adoption of ASC 842, we increased our total assets and liabilities due to the recording of operating lease ROU assets and operating lease liabilities of approximately $50.8 million and $63.7 million , respectively, as of January 1, 2019. These increases did not have a material impact on our results of operations or cash flows. For all leases that commenced before the effective date of ASC 842, we elected to apply the permitted practical expedients to not reassess the following: (1) whether any expired or existing contracts contain leases; (2) the lease classification for any expired or existing leases; and (3) initial direct costs for any existing leases. We determine if an arrangement is a lease at inception of a contract. ROU assets represent our right to use an underlying asset for the lease term and lease liabilities represent our obligation to make lease payments arising from the lease. ROU assets and lease liabilities are recognized at the lease commencement date based on the present value of lease payments over the lease term. As most of our leases do not provide an implicit interest rate, we use our incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The lease terms used to calculate the ROU asset and related lease liability include options to extend or terminate the lease when it is reasonably certain that we will exercise that option. Lease expense for operating leases is recognized on a straight-line basis over the lease term as an operating expense. We have lease agreements which require payments for lease and non-lease components and have elected to account for these as a single lease component related to our other operating facilities.

Accounting Policies (Tables)

Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Activity and balances related to incurred but not paid workers' compensation claims	The following table provides the activity and balances related to incurred but not paid workers’ compensation claims: Six Months Ended June 30, (in thousands) 2019 2018 Beginning balance, January 1, $ 229,639 $ 207,630 Accrued claims 27,299 33,260 Present value discount (2,703 ) (3,360 ) Paid claims (22,727 ) (21,686 ) Ending balance $ 231,508 $ 215,844 Current portion of accrued claims $ 43,267 $ 41,827 Long-term portion of accrued claims 188,241 174,017 Total accrued claims $ 231,508 $ 215,844
Disaggregation of Revenue [Table Text Block]	Our revenue for our PEO HR Outsourcing solutions by geographic region and for our other products and services offerings are as follows: Three Months Ended June 30, Six Months Ended June 30, (in thousands) 2019 2018 % Change 2019 2018 % Change Northeast $ 270,475 $ 239,278 13.0 % $ 581,422 $ 511,642 13.6 % Southeast 120,148 108,264 11.0 % 250,054 223,452 11.9 % Central 179,443 153,025 17.3 % 375,196 321,092 16.8 % Southwest 244,462 213,920 14.3 % 514,294 446,785 15.1 % West 215,639 194,986 10.6 % 448,842 407,605 10.1 % 1,030,167 909,473 13.3 % 2,169,808 1,910,576 13.6 % Other revenue 13,149 12,822 2.6 % 26,518 26,091 1.6 % Total revenue $ 1,043,316 $ 922,295 13.1 % $ 2,196,326 $ 1,936,667 13.4 %

Cash, Cash Equivalents and Ma_2

Cash, Cash Equivalents and Marketable Securities (Tables)	6 Months Ended
	Jun. 30, 2019
Cash, Cash Equivalents and Marketable Securities [Abstract]
Summary of investments in 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: June 30, 2019 December 31, 2018 (in thousands) Cash & Cash Equivalents Marketable Securities Total Cash & Cash Equivalents Marketable Securities Total Overnight holdings $ 292,464 $ — $ 292,464 $ 311,158 $ — $ 311,158 Investment holdings 13,515 61,129 74,644 16,711 60,781 77,492 Cash in demand accounts 39,915 — 39,915 33,207 — 33,207 Outstanding checks (20,968 ) — (20,968 ) (34,303 ) — (34,303 ) Total $ 324,926 $ 61,129 $ 386,055 $ 326,773 $ 60,781 $ 387,554

Fair Value Measurements Fair _2

Fair Value Measurements Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Table Text Block]	The following table summarizes the levels of fair value measurements of our financial assets: June 30, 2019 December 31, 2018 (in thousands) Total Level 1 Level 2 Total Level 1 Level 2 Money market funds $ 303,908 $ 303,908 $ — $ 325,819 $ 325,819 $ — U.S. Treasury bills 59,775 59,775 — 52,197 52,197 — Municipal bonds 3,425 — 3,425 10,634 — 10,634 Total $ 367,108 $ 363,683 $ 3,425 $ 388,650 $ 378,016 $ 10,634
Available-for-sale Securities [Table Text Block]	The following is a summary of our available-for-sale marketable securities: (in thousands) Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value June 30, 2019 U.S. Treasury bills $ 57,650 $ 54 $ — $ 57,704 Municipal bonds 3,425 — — 3,425 Total $ 61,075 $ 54 $ — $ 61,129 December 31, 2018 U.S. Treasury bills $ 50,150 $ — $ (3 ) $ 50,147 Municipal bonds 10,640 1 (7 ) 10,634 Total $ 60,790 $ 1 $ (10 ) $ 60,781
Investments Classified by Contractual Maturity Date [Table Text Block]	As of June 30, 2019 , the contractual maturities of our marketable securities were as follows: (in thousands) Amortized Cost Estimated Fair Value Less than one year $ 61,075 $ 61,129 One to five years — — Total $ 61,075 $ 61,129

Leases Leases (Tables)

Leases Leases (Tables)	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Schedule of lease in balance sheet [Table Text Block]	The following table presents the lease balances within our Condensed Consolidated Balance Sheets, weighted average lease term and weighted average discount rates related to our operating leases: (dollars in thousands) Classification in Condensed Consolidated Balance Sheets June 30, 2019 Operating lease ROU assets Right-of-use leased assets $ 54,189 Lease liabilities: Current operating lease liabilities Other accrued liabilities $ 14,241 Long-term operating lease liabilities Operating lease liabilities, net of current 54,617 Total operating lease liabilities $ 68,858 Less: Landlord funded tenant improvements $ 10,555 Deferred rent 4,114 Operating lease ROU assets $ 54,189 Weighted average remaining lease term (years) 6 Weighted average discount rate 4.7 %
Lessee, Operating Lease, Liability, Maturity [Table Text Block]	The following presents the maturity of our operating leases liabilities as of June 30, 2019 : (in thousands) Operating Leases Remainder of 2019 $ 8,578 2020 16,035 2021 13,185 2022 11,637 2023 9,286 Thereafter 20,606 Total remaining obligation 79,327 Less imputed interest 10,469 Present value of lease liabilities $ 68,858

Stockholders' Equity Stockholde

Stockholders' Equity Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2019
Stockholders' Equity Attributable to Parent [Abstract]
Quarterly dividends declared [Table Text Block]	The Board declared quarterly dividends as follows: (amounts per share) 2019 2018 First quarter $ 0.30 $ 0.20 Second quarter 0.30 0.20

Net Income per Share (Tables)

Net Income per Share (Tables)	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Summary of the net income allocated to common shares and the basic and diluted shares used in the net income per share computations	The following table summarizes the net income allocated to common shares and the basic and diluted shares used in the net income per share computations: Three Months Ended June 30, Six Months Ended (in thousands) 2019 2018 2019 2018 Net income $ 28,556 $ 24,560 $ 104,845 $ 74,551 Less distributed and undistributed earnings allocated to participating securities (309 ) (346 ) (1,183 ) (1,064 ) Net income allocated to common shares $ 28,247 $ 24,214 $ 103,662 $ 73,487 Weighted average common shares outstanding 40,771 41,377 40,640 41,301 Incremental shares from assumed LTIP awards and conversions of common stock options 145 156 140 324 Adjusted weighted average common shares outstanding 40,916 41,533 40,780 41,625

Accounting Policies (Details)

Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Health Insurance Costs [Abstract]
Percentage of our health insurance coverage provided by United	87.00%		87.00%
Number of days in advance of the beginning of a reporting quarter United establishes cash funding rates			90 days
Required accumulated cash surplus	$ 9,000		$ 9,000		$ 9,000
Required deposit equal to approximately one day of claims funding activity	5,000		5,000
Amount which plan costs were less than the net premiums paid and owed	16,400		16,400
Prepaid health insurance, current	7,400		7,400
Premiums owed to United	15,000		15,000
Benefits costs incurred (reduced) related to run-off	(3,500)		(3,500)
Workers' Compensation Costs [Abstract]
Company's maximum economic burden for the first layer of claims per occurrence	1,000		1,000
Company's maximum aggregate economic burden for claims in excess of 1 million per policy year	6,000		6,000
Decrease Increase in accrued workers' compensation costs for changes in estimated losses			$ 19,000	$ 10,900
U.S. Treasury rates that correspond with the weighted average estimated claim payout period (in hundredths)			2.30%	2.50%
Incurred but not paid workers compensation liabilities [Abstract]
Workers' Compensation Expense			$ 27,299	$ 33,260
Present value discount			(2,703)	(3,360)
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid			(22,727)	(21,686)
Ending balance	231,508	$ 215,844	231,508	215,844
Long-term portion of accrued claims	188,241	174,017	188,241	174,017	187,412
Workers compensation administrative fees accrued	3,900		3,900
Undiscounted accrued workers' compensation costs			$ 250,900	230,400
Time period incurred claims expected to be paid recorded as restricted cash			1 year
Time period incurred claims expected to be paid, included in deposits, a long-term asset			Greater than 1 year
Restricted cash	43,268	41,827	$ 43,268	41,827	42,227	$ 41,137
Deposits workers compensation	187,728	165,150	$ 187,728	165,150	166,474	154,215
Time period estimate of incurred claim costs to be paid included in short-term liabilities			1 year
Time period incurred claims expected to be paid, included in long-term liabilities			Greater than 1 year
Unbilled	414,600		$ 414,600		385,600
Disaggregation of Revenue [Line Items]
WorkersCompensationLiabilityNetOfAdminFeesCurrent	43,267	41,827	43,267	41,827
Liability for Unpaid Claims and Claims Adjustment Expense, Adjustments	231,508	215,844	231,508	215,844	$ 229,639	$ 207,630
Revenue from Contract with Customer, Excluding Assessed Tax	1,043,316	922,295	2,196,326	1,936,667
Northeast [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	270,475	239,278	581,422	511,642
Southeast [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	120,148	108,264	250,054	223,452
Central [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	179,443	153,025	375,196	321,092
Southwest [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	244,462	213,920	514,294	446,785
West [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	215,639	194,986	448,842	407,605
Other Revenues [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 13,149	$ 12,822	$ 26,518	$ 26,091

Cash, Cash Equivalents and Ma_3

Cash, Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Line Items]
Overnight Holdings	$ 292,464	$ 311,158
Short-term Investments	74,644	77,492
Cash	39,915	33,207
Drafts Payable	(20,968)	(34,303)
Cash, Cash Equivalents, and Short-term Investments	386,055	387,554
Payroll Withholdings Included in Cash Balance	218,000	224,500
Client Prepayments Included in Cash Balance	37,400	34,200
Money Market Funds [Member]
Cash and Cash Equivalents [Line Items]
Overnight Holdings	0	0
Short-term Investments	61,129	60,781
Cash	0	0
Drafts Payable	0	0
Cash, Cash Equivalents, and Short-term Investments	61,129	60,781
Cash and Cash Equivalents [Member]
Cash and Cash Equivalents [Line Items]
Overnight Holdings	292,464	311,158
Short-term Investments	13,515	16,711
Cash	39,915	33,207
Drafts Payable	(20,968)	(34,303)
Cash, Cash Equivalents, and Short-term Investments	$ 324,926	$ 326,773

Fair Value Measurements Fair _3

Fair Value Measurements Fair Value Measurements (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	$ 303,908	$ 325,819
US Government Securities, at Carrying Value	59,775	52,197
Municipal bonds	3,425	10,634
Total	367,108	388,650
Available-for-sale Securities, Amortized Cost Basis	61,075	60,790
Available-for-sale Securities, Gross Unrealized Gain	54	1
Available-for-sale Securities, Gross Unrealized Loss	0	(10)
Available-for-sale Securities	61,129	60,781
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost	61,075
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Amortized Cost	0
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value	61,129
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, after One Through Five Years, Fair Value	0
US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Amortized Cost Basis	57,650	50,150
Available-for-sale Securities, Gross Unrealized Gain	54	0
Available-for-sale Securities, Gross Unrealized Loss	0	(3)
Available-for-sale Securities	57,704	50,147
Municipal Bond [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Amortized Cost Basis	3,425	10,640
Available-for-sale Securities, Gross Unrealized Gain	0	1
Available-for-sale Securities, Gross Unrealized Loss	0	(7)
Available-for-sale Securities	3,425	10,634
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	303,908	325,819
US Government Securities, at Carrying Value	59,775	52,197
Municipal bonds	0	0
Total	363,683	378,016
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	0	0
US Government Securities, at Carrying Value	0	0
Municipal bonds	3,425	10,634
Total	$ 3,425	$ 10,634

Long-term Debt (Details)

Long-term Debt (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)	Dec. 31, 2018USD ($)
Line of Credit Facility [Line Items]
Current borrowing capacity	$ 350,000
Maximum borrowing capacity	$ 400,000
Percentage Of Subsidiary Stock Securing Debt	0.65
Long-term debt	$ 169,400	$ 144,400
Letters of Credit Outstanding, Amount	1,000
Line of Credit Facility, Remaining Borrowing Capacity	$ 179,600
Applicable Margin Federal Funds Rate	0.50%
Applicable Margin 30 Day Libor	2.00%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.25%
Line of Credit Facility, Interest Rate During Period	4.00%
London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.50%
London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.25%
Base Rate [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.00%
Base Rate [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.50%

Leases Leases (Details)

Leases Leases (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Operating Lease, Cost	$ 3,800	$ 7,600
Operating Lease, Payments		8,100
Lessee Operating Lease Leases Not Yet Commenced Amount	16,600	16,600
Right-of-use leased assets	$ 54,189	$ 54,189	$ 50,800	$ 0
Operating Lease, Weighted Average Remaining Lease Term	6 years	6 years
Operating Lease, Liability, Current	$ 14,241	$ 14,241
Operating lease liabilities, net of current	54,617	54,617		$ 0
Landlord funded tenant improvements	10,555	10,555
Deferred Rent Credit, Noncurrent	$ 4,114	$ 4,114
Operating Lease, Weighted Average Discount Rate, Percent	4.70%	4.70%
Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year	$ 8,578	$ 8,578
Lessee, Operating Lease, Liability, Payments, Due Year Two	16,035	16,035
Lessee, Operating Lease, Liability, Payments, Due Year Three	13,185	13,185
Lessee, Operating Lease, Liability, Payments, Due Year Four	11,637	11,637
Lessee, Operating Lease, Liability, Payments, Due Year Five	9,286	9,286
Lessee, Operating Lease, Liability, Payments, Due after Year Five	20,606	20,606
Lessee, Operating Lease, Liability, Payments, Due	79,327	79,327
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	10,469	10,469
Operating Lease, Liability	$ 68,858	$ 68,858	$ 63,700
Minimum [Member]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract	4 years	4 years
Maximum [Member]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract	7 years	7 years

Stockholders' Equity (Details)

Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Stockholders' Equity Note [Abstract]
Dividends					$ 24.7	$ 16.8
Aggregate number of shares repurchased during the period (in shares)					315,369
Shares repurchased under the program (in shares)					88,210
Authorized to repurchased additional shares under repurchase program (in shares)	1,522,945				1,522,945
Shares withheld for tax withholding obligations for the vesting of restricted stock awards (in shares)					227,159
Dividends declared per share of common stock (in dollars per share)	$ 0.30	$ 0.30	$ 0.20	$ 0.20

Net Income per Share (Details)

Net Income per Share (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Net income	$ 28,556	$ 24,560	$ 104,845	$ 74,551
Less distributed and undistributed earnings allocated to participating securities	309	346	1,183	1,064
Net Income (Loss) Available to Common Stockholders, Basic	$ 28,247	$ 24,214	$ 103,662	$ 73,487
Weighted average common shares outstanding basic (in shares)	40,771	41,377	40,640	41,301
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	145	156	140	324
Weighted Average Number of Shares Outstanding, Diluted	40,916	41,533	40,780	41,625

Commitments and Contingencies C

Commitments and Contingencies Commitments and Contingencies (Details)	6 Months Ended
	Jun. 30, 2019USD ($)
Commitments and Contingencies Disclosure (Details) [Abstract]
Loss Contingency, Damages Sought	$ 128,000,000
Loss Contingency Accrual, Provision	$ 0