Securities Financing Including Redeemable Preferred Stocks- Summary of Redeemable Preferred Stock (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2016
Stockholders Equity [Line Items]
Accumulated dividend		$ 14,979
Series E Redeemable Preferred Stock [Member]
Stockholders Equity [Line Items]
Beginning balance		$ 177,272
Beginning balance, shares		210,000
Accretion relating to liquidation preference on preferred stock		$ 1,448
Accretion for discount and issuance costs on preferred stock		3,036
Accumulated dividend	$ 7,629	14,979
Ending balance	$ 196,735	$ 196,735
Ending balance, shares	210,000	210,000
Series F Redeemable Preferred Stock [Member]
Stockholders Equity [Line Items]
Beginning balance, shares		1
Ending balance, shares	1	1