Capitalized Servicing Assets - Changes in Capitalized Servicing Assets (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Servicing Asset at Amortized Cost [Line Items]
Amortized value, Beginning balance	$ 210,101	$ 172,976	$ 198,192
Originations	44,207	79,129	34,230
Purchases	1,019	272	109
Recognized in loan securitization transactions		23,078
Amortization	(68,410)	(65,354)	(59,555)
Amortized value, ending balance	186,917	210,101	172,976
Valuation allowance		(300)	(4,500)
Ending balance, net	186,917	209,801	168,476
Other [Member]
Servicing Asset at Amortized Cost [Line Items]
Amortized value, Beginning balance	11,225	8,143	15,678
Recognized in loan securitization transactions		9,382
Amortization	(7,118)	(6,300)	(7,535)
Amortized value, ending balance	4,107	11,225	8,143
Ending balance, net	4,107	11,225	8,143
Residential Mortgage Loans [Member]
Servicing Asset at Amortized Cost [Line Items]
Amortized value, Beginning balance	126,377	104,855	131,264
Originations	28,285	52,375	14,577
Purchases	289	272	109
Recognized in loan securitization transactions		13,696
Amortization	(45,080)	(44,821)	(41,095)
Amortized value, ending balance	109,871	126,377	104,855
Valuation allowance		(300)	(4,500)
Ending balance, net	109,871	126,077	100,355
Commercial Mortgage Loans [Member]
Servicing Asset at Amortized Cost [Line Items]
Amortized value, Beginning balance	72,499	59,978	51,250
Originations	15,922	26,754	19,653
Purchases	730
Amortization	(16,212)	(14,233)	(10,925)
Amortized value, ending balance	72,939	72,499	59,978
Ending balance, net	$ 72,939	$ 72,499	$ 59,978