Acquisitions (First quarter 2015) - Additional Information (Detail) $ in Millions		3 Months Ended		6 Months Ended
	Mar. 01, 2015 USD ($)	Jun. 30, 2015 USD ($) Business Client_List	Mar. 31, 2015 USD ($) Business Client_List	Jun. 30, 2015 USD ($)
Business Acquisition, Contingent Consideration [Line Items]
Contingent consideration		$ 4.2		$ 4.2
Model Consulting, Inc [Member]
Business Acquisition, Contingent Consideration [Line Items]
Consideration paid in cash			$ 5.5
Number of businesses acquired | Business			1
Contingent consideration			$ 4.2
Annual revenue	$ 4.2
Acquired entity, name	Model Consulting, Inc
Effective date of acquisition				Mar. 01, 2015
Acquisition of Client Lists [Member]
Business Acquisition, Contingent Consideration [Line Items]
Consideration paid in cash		$ 3.0	0.1
Number of businesses acquired | Business		0
Guaranteed future consideration			$ 0.3
Acquisition of Client Lists [Member] | Employee Services [Member]
Business Acquisition, Contingent Consideration [Line Items]
Number of client list purchased | Client_List		1	2