Schedule of Share-based Compensation Expense (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	$ 7,061	[1]	$ 10,138	[1]	$ 8,432	[1]
Income tax benefit	2,698	[1]	4,101	[1]	3,104	[1]
Share-based compensation, net of income taxes	4,363	[1]	6,037	[1]	5,328	[1]
Stock Options | Direct Cost Of Revenues
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	5,404	[1]	6,807	[1]	6,012	[1]
Stock Options | Selling, General And Administrative Expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	1,783	[1]	1,849	[1]	1,836	[1]
Stock Options | Special Charges
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	(126)	[1],[2]	1,482	[1],[2]	584	[1],[2]
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	16,469	[3],[4]	25,172	[3],[4]	20,577	[3],[4]
Income tax benefit	6,490	[3],[4]	9,094	[3],[4]	6,870	[3],[4]
Share-based compensation, net of income taxes	9,979	[3],[4]	16,078	[3],[4]	13,707	[3],[4]
Restricted Stock | Direct Cost Of Revenues
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	8,951	[3],[4]	9,181	[3],[4]	10,000	[3],[4]
Restricted Stock | Selling, General And Administrative Expense
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	8,508	[3],[4]	10,053	[3],[4]	10,347	[3],[4]
Restricted Stock | Special Charges
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based compensation expense	$ (990)	[2],[3],[4]	$ 5,938	[2],[3],[4]	$ 230	[2],[3],[4]

[1] Includes options and cash-settled stock appreciation rights.

[2] Special charges of $0.2 million equity award expense acceleration and $0.1 million option expense acceleration are net of forfeitures of $1.2 million and $0.2 million, respectively, for the year ended December 31, 2014. (See Note 4 to the Consolidated Financial Statements for information related to the special charges).

[3] Includes cash-settled restricted stock units.

[4] Includes restricted share awards and performance and market condition restricted share units.