Commitments and Contingent liabilities - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended	0 Months Ended		0 Months Ended		0 Months Ended
	Aug. 06, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 lawsuit director	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 Operating lease expense [Member]	Sep. 30, 2012 Operating lease expense [Member]	Sep. 30, 2013 Operating lease expense [Member]	Sep. 30, 2012 Operating lease expense [Member]	Jun. 30, 2012 Facebook IPO [Member]	Apr. 02, 2013 Facebook IPO [Member]	Mar. 22, 2013 Facebook IPO [Member]	Apr. 02, 2013 Customer [Member] Facebook IPO [Member]	Sep. 30, 2013 Customer [Member] Facebook IPO [Member]	Apr. 02, 2013 Parent Company [Member] Facebook IPO [Member]	Sep. 30, 2013 Revolving Credit Facility [Member]
Component of Operating Other Cost and Expense [Line Items]
Number of putative class action lawsuits				2
Number of derivative lawsuits				1
Raise In equity financing	$ 400,000,000
Number of directors accused of breaking fiduciary duties				7
Pre-tax loss settlements realized						457,600,000
Restructuring charge											35,400,000
Claims limitation related to IPO													62,000,000
Claims submitted												13,000,000		2,600,000		10,400,000
Percentage claimed less than submitted															17.00%
Weighted average interest rate																	3.85%
Rental expense		8,898,000	3,240,000	15,454,000	8,865,000		5,600,000	2,300,000	10,400,000	6,400,000
Letters of credit held in escrow		1,000,000		1,000,000
Additional borrowing capacity due to issuance of HECMs				$ 726,000,000
Debt term				3 years