Debt - Additional Information 4 (Detail) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	1 Months Ended	3 Months Ended	9 Months Ended				0 Months Ended		1 Months Ended	3 Months Ended	9 Months Ended	0 Months Ended		1 Months Ended	9 Months Ended
	Aug. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2012	Jul. 02, 2013 Janus Holdings [Member]	Jul. 02, 2013 Cabot Credit Management [Member] Janus Holdings [Member]	Nov. 27, 2012 2017 Convertible Senior Notes [Member]	Jun. 30, 2012 2017 Convertible Senior Notes [Member]	Nov. 27, 2012 2017 Convertible Senior Notes [Member]	Sep. 30, 2013 2017 Convertible Senior Notes [Member]	Sep. 30, 2013 2017 Convertible Senior Notes [Member]	Jul. 18, 2013 2020 Convertible Senior Notes [Member]	Jun. 24, 2013 2020 Convertible Senior Notes [Member]	Jun. 24, 2013 2020 Convertible Senior Notes [Member]	Sep. 30, 2013 2020 Convertible Senior Notes [Member]	Sep. 30, 2013 Computer equipment [Member]
Debt Instrument [Line Items]
Proceeds from issuance of additional convertible senior notes			$ 172,500,000				$ 100,000,000	$ 15,000,000				$ 22,500,000	$ 150,000,000
Interest rate of PEC		12.00%	12.00%				3.00%		3.00%				3.00%	3.00%
Maturity date of 3.0% convertible senior notes							Nov. 27, 2017						Jul. 01, 2020
Convertible senior notes outstanding		287,500,000	287,500,000	115,000,000			115,000,000		115,000,000			172,500,000
Debt instrument interest payment date											Interest on the 2017 Convertible Notes is payable semi-annually, in arrears, on May 27 and November 27 of each year				Interest on the 2020 Convertible Notes is payable semi-annually, in arrears, on January 1 and July 1 of each year
Initial conversion rate									31.6832					21.8718
Convertible senior notes, principal amount							1,000		1,000				1,000	1,000
Initial conversion price per share							$ 31.56		$ 31.56	$ 31.56	$ 31.56		$ 45.72	$ 45.72
Dilutive effect of convertible senior notes		805	298							800	300
Strike price of the Warrant Transactions per share											$ 44.1875
Effective conversion price of Notes per share										$ 44.1875	$ 44.1875
Average share price of common stock										$ 44.1875	$ 44.1875
Capped Call Transactions cost															18,100,000
Cap price of capped call transactions per share															$ 61.5475
Proceeds from sale of Notes															167,400,000
Net proceeds used for payment of convertible note hedge transaction cost															18,100,000
Fair value of notes															140,200,000
Residual value		46,954,000	46,954,000	14,702,000											32,300,000
Debt issuance cost															4,900,000
Initial debt issuance costs															6,000,000
Equity issuance cost															1,100,000
Effective interest rate on the liability component										6.00%	6.00%				6.35%
Percentage of equity interest acquired						50.10%
Minority interest percentage					49.90%
Repayment of J Bridge PECs	41,200,000
Preferred equity certificates		190,279,000	190,279,000
Capital lease obligations		$ 6,920,000	$ 6,920,000	$ 9,252,000												$ 6,900,000
Capital lease obligations, minimum percentage			0.00%
Capital lease obligations, maximum percentage			7.70%