Capitalized Servicing Assets - Changes in Capitalized Servicing Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Servicing Asset at Amortized Cost [Line Items]
Amortized value, Beginning balance	$ 202,724	$ 186,917	$ 210,101
Originations	68,735	65,470	44,207
Purchases	638	243	1,019
Amortization	(50,982)	(49,906)	(68,410)
Amortized value, ending balance	221,115	202,724	186,917
Ending balance, net	221,115	202,724	186,917
Residential Mortgage Loans [Member]
Servicing Asset at Amortized Cost [Line Items]
Amortized value, Beginning balance	118,303	109,871	126,377
Originations	28,618	35,556	28,285
Purchases	638	243	289
Amortization	(30,208)	(27,367)	(45,080)
Amortized value, ending balance	117,351	118,303	109,871
Ending balance, net	117,351	118,303	109,871
Commercial Mortgage Loans [Member]
Servicing Asset at Amortized Cost [Line Items]
Amortized value, Beginning balance	83,692	72,939	72,499
Originations	40,117	29,914	15,922
Purchases			730
Amortization	(20,045)	(19,161)	(16,212)
Amortized value, ending balance	103,764	83,692	72,939
Ending balance, net	103,764	83,692	72,939
Other [Member]
Servicing Asset at Amortized Cost [Line Items]
Amortized value, Beginning balance	729	4,107	11,225
Amortization	$ (729)	(3,378)	(7,118)
Amortized value, ending balance		729	4,107
Ending balance, net		$ 729	$ 4,107