Securities Financing Including Redeemable Preferred Stocks- Summary of Redeemable Preferred Stock (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($) shares
Stockholders Equity [Line Items]
Accumulated dividend	$ 7,350
Series E Redeemable Preferred Stock [Member]
Stockholders Equity [Line Items]
Beginning balance	$ 177,272
Beginning balance, shares | shares	210,000
Accretion relating to liquidation preference on preferred stock	$ 725
Accretion for discount and issuance costs on preferred stock	1,518
Accumulated dividend	7,350
Ending balance	$ 186,865
Ending balance, shares | shares	210,000
Series F Redeemable Preferred Stock [Member]
Stockholders Equity [Line Items]
Beginning balance, shares | shares	1
Ending balance, shares | shares	1