Goodwill and Intangibles, net - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Goodwill And Intangible Assets [Line Items]
Goodwill increased (decreased) amount					$ 20,000,000
Acquisition of Superior Access, estimated goodwill	1,200,000		1,200,000
Amortization of intangible assets	2,176,000	1,511,000	6,211,000	3,318,000
Subsidiaries
Goodwill And Intangible Assets [Line Items]
Amortization of intangible assets	2,200,000	1,500,000	6,200,000	3,300,000
Bolt
Goodwill And Intangible Assets [Line Items]
Goodwill increased (decreased) amount					10,200,000
Amortization of intangible assets	600,000		1,700,000
Decrease in intangible assets			10,900,000
ICG
Goodwill And Intangible Assets [Line Items]
Goodwill increased (decreased) amount	(800,000)				10,200,000
Additiona paid in capital increase (decrease) amount	(800,000)
Decrease in intangible assets			23,000,000
Procurian
Goodwill And Intangible Assets [Line Items]
Goodwill increased (decreased) amount					(30,200,000)
Decrease in intangible assets			$ 12,100,000