Commitments and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Other Commitments [Line Items]
Operating lease, rental expense	$ 5,600,000	$ 5,300,000	$ 5,200,000
Purchase commitment, total	12,600,000
Commitments to be paid in 2015	7,600,000
Commitments to be paid in 2016	4,000,000
Commitments to be paid in 2017	1,000,000
Commitments to be paid in 2018	11,000
Commitments to be paid in 2019	0
Letter of credit outstanding, for workers compensation	2,700,000
Letter of credit outstanding, for facility lease deposit	500,000
Provision for litigation loss		0
Tax audit cost		0
Severance Payment Under Agreement Description	Certain of the agreements also provide for a severance payment of one to three times annual salary and one half to three times average annual bonus if such an agreement is terminated without good cause by the employer or for good reason by the employee.
Employees under contract terminated by employer without good cause or change in control	19,200,000
Employees under contract terminated by employer without good cause or in absence of change in control	$ 41,600,000
Minimum [Member]
Other Commitments [Line Items]
Tenure of expiration of lease	30 days
Period for providing minimum compensation salary and continuation of certain benefits to executives under employment agreements	6 months
Severance payment as a percentage of annual salary	100.00%
Severance payment as a percentage of annual bonus	50.00%
Maximum [Member]
Other Commitments [Line Items]
Tenure of expiration of lease	90 days
Period for providing minimum compensation salary and continuation of certain benefits to executives under employment agreements	3 years
Severance payment as a percentage of annual salary	300.00%
Severance payment as a percentage of annual bonus	300.00%