Equity Method Investments - Summary of Abacus' Income Statement Information (Detail) (Abacus [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Abacus [Member]
Schedule Of Equity Method Investments [Line Items]
Revenue	$ 87,039	$ 83,237	$ 263,536	$ 248,814
Operating income	12,876	15,946	42,961	41,683
Net income	$ 10,793	$ 8,887	$ 34,863	$ 30,575