Acquisitions (Details 3) (USD $)	3 Months Ended		9 Months Ended		1 Months Ended	3 Months Ended	12 Months Ended		21 Months Ended			1 Months Ended	9 Months Ended		1 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Jul. 31, 2009 Nitro Limited [Member]	Mar. 31, 2011 Nitro Limited [Member]	Dec. 31, 2010 Nitro Limited [Member]	Dec. 31, 2009 Nitro Limited [Member]	Mar. 31, 2011 Nitro Limited [Member]	Sep. 30, 2011 Nitro Limited [Member]	Jul. 01, 2009 Nitro Limited [Member] Person	Sep. 30, 2011 D&D Holdings Limited [Member]	Sep. 30, 2011 D&D Holdings Limited [Member]	Sep. 06, 2011 D&D Holdings Limited [Member] Person	Jul. 31, 2011 Clanmo GmbH [Member]	Sep. 30, 2011 Clanmo GmbH [Member]	Sep. 30, 2011 Clanmo GmbH [Member]	Jul. 13, 2011 Clanmo GmbH [Member] Person
Acquisitions (Textual) [Abstract]
Date of acquisition					2009-07-01							2011-09-06			2011-07-13
Approximate number of employees added via acquisition											300			200				50
Percentage of outstanding shares acquired											100.00%			100.00%	100.00%
Acquisition, purchase price, net of cash acquired											$ 31,000,000			$ 45,200,000	$ 5,400,000
Additional consideration												21,100,000	21,100,000
Acquisition, cash paid, net of cash acquired											11,100,000			29,500,000
Estimated fair value of deferred consideration											8,100,000			15,700,000
Number of shares issued as consideration in business acquisition					3,300,000
Value of stock issued as consideration in business acquisition											11,800,000
Value of common stock per share on the acquisition date											$ 6.27
Reduction in business acquisition purchase price allocation to common stock value due to selling restrictions on shares and sellers continued employment											8,700,000
Business acquisition value of shares transferred with selling restrictions											7,100,000
Equity transferred for continued employment of seller					1,600,000
Share-based compensation expense	5,018,000	4,289,000	14,237,000	13,924,000		1,000,000			1,600,000
Acquisition of deferred consideration obligation											8,000,000
Limit over which the seller agreed to indemnify the Company											8,000,000
Cash paid to settle deferred consideration obligation							3,200,000	4,600,000
Deferred consideration obligation										1,300,000
Liabilities recorded for contingent consideration												15,000,000	15,000,000	15,700,000
Indemnification asset										1,100,000
Value of rights shares issued in acquisition													3,900,000
Vesting period for Stock Option													3 years
Service revenues	262,730,000	217,057,000	758,686,000	600,631,000									2,000,000			1,600,000
Net income	19,102,000	14,275,000	46,464,000	28,118,000									(400,000)			200,000
Acquisition costs and other related charges	1,082,000		1,305,000	111,000												1,100,000	1,300,000
Purchase price placed in escrow agreement														$ 9,800,000	$ 600,000