Debt and Financing Arrangements (2010 Notes) - Additional Information (Detail) - USD ($)		1 Months Ended	3 Months Ended												9 Months Ended	12 Months Ended
	Oct. 01, 2015	Oct. 30, 2015	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	[1]	Sep. 30, 2015	[1]	Jun. 30, 2015		Mar. 31, 2015	[1]	Sep. 30, 2014	Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Debt Instrument [Line Items]
Non operating charge included in other income, net			$ 1,475,000	$ 2,632,000	$ 703,000	$ 2,147,000	$ 1,780,000		$ (2,367,000)		$ (1,126,000)	[1]	$ 2,859,000			$ 6,957,000	$ 1,146,000	[2]	$ 6,893,000
Other Income [Member]
Debt Instrument [Line Items]
Non operating charge included in other income, net																	$ 800,000		$ 1,500,000
2010 Convertible Senior Subordinated Notes [Member]
Debt Instrument [Line Items]
Notes payable outstanding			0													0
Principal amount of notes			$ 48,400,000													$ 48,400,000
Conversion rate per $ 1,000 principal of convertible notes	$ 1,000
Conversion value of Notes		$ 71,800,000
Maturity date of notes																Oct. 01, 2015
Shares issued in exchange for partial retirement of debt											5,100,000				1,500,000
Partial extinguishment of debt											$ 49,300,000				$ 32,400,000
Common stock equivalent impact																0	1,200,000		2,000,000

[1] “Operating expenses” and “Corporate general and administrative expenses” include a reduction ($1.6 million and less than $0.1 million) related to a state payroll tax incentive associated with an office relocation. The reduction was recorded in “Other (expense) income, net” beginning in the third quarter of 2015, but was reclassified to “Operating expenses” and “Corporate general and administrative expenses” to align the incentives with the expenses associated with the office relocation. The reclassification had no impact on “Income from continuing operations” or diluted earnings per share from continuing operations.

[2] “Operating expenses” under the Financial Services and Benefits and Insurance Services practice groups include a reduction of $0.9 million and $0.6 million related to a state payroll tax incentive associated with an office relocation. “Corporate general and administrative expenses” include a reduction of less than $0.1 million related to the office relocation as discussed above. The reductions was recorded in “Other (expense) income, net” in 2015 but was reclassified to “Operating expenses” and “Corporate general and administrative expenses” to align the incentives with the expenses associated with the office relocation. The reclassification had no impact on “Income from continuing operations” or diluted earnings per share from continuing operations.