Commitments and Contingencies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) property	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Operating Leases
2017	$ 19,458
2018	17,719
2019	14,200
2020	11,660
2021	9,084
Thereafter	10,742
Total	82,863
Related Party
2017	1,169
2018	1,302
2019	1,282
2020	1,314
2021	1,347
Thereafter	3,999
Total	10,413
Purchase Obligation, Due in Next Twelve Months	8,694
Purchase Obligation, Due in Second Year	4,121
Purchase Obligation, Due in Third Year	1,255
Purchase Obligation, Due in Fourth Year	0
Purchase Obligation, Due in Fifth Year	0
Purchase Obligation, Due after Fifth Year	0
Purchase Obligation	14,070
Total
2017	29,321
2018	23,142
2019	16,737
2020	12,974
2021	10,431
Thereafter	14,741
Total	107,346
Deferred Rent Credit, Current	600	$ 500
Deferred rent liability, noncurrent	5,200	4,300
Rent expense	25,600	21,600	$ 17,600
Costs and Expenses, Related Party	1,300	1,300	$ 1,300
Self Insurance Reserve	1,800	1,800
Workerscompensationreceivable	14,001	13,238
Letters of credit outstanding	$ 4,000	$ 3,500
Apex Systems
Total
Number of leased properties owned by related parties (in number of properties) | property	2