Segment Information - Components of Corporate/Other (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting Information [Line Items]
Interest income		$ 63,373	$ 57,993	$ 127,119	$ 113,469
Interest expense		(23,008)	(21,151)	(46,969)	(40,211)
Net Interest Income		40,365	36,842	80,150	73,258
Provision for loan losses		261	315	55	(967)
Mortgage banking and investment activities	[1]	5,659	2,189	6,437	(4,181)
MSR income (loss), net		830	(1,777)	(10,094)	(1,171)
Realized gains, net		6,316	1,063	10,622	2,155
Total noninterest income, net		14,104	1,475	9,073	(3,197)
Direct operating expenses		(25,218)	(22,282)	(50,281)	(42,254)
Benefit from income taxes		(2,448)	(333)	2,868	1,510
Net income		27,064	16,017	41,865	28,350
Legacy Consolidated VIEs
Segment Reporting Information [Line Items]
Interest income		6,462	6,411	13,480	13,240
Interest expense		(4,048)	(5,240)	(8,530)	(10,699)
Net Interest Income		2,414	1,171	4,950	2,541
Provision for loan losses		0	604	0	(23)
Mortgage banking and investment activities		(684)	(321)	(1,777)	(464)
MSR income (loss), net		0	0	0	0
Realized gains, net		0	71	0	176
Total noninterest income, net		(684)	(250)	(1,777)	(288)
Direct operating expenses		0	(42)	0	(94)
Benefit from income taxes		0	0	0	0
Net income		1,730	1,483	3,173	2,136
Other
Segment Reporting Information [Line Items]
Interest income		7	3	14	5
Interest expense		(9,505)	(6,230)	(18,908)	(12,356)
Net Interest Income		(9,498)	(6,227)	(18,894)	(12,351)
Provision for loan losses		0	0	0	0
Mortgage banking and investment activities		0	(25)	(36)	(61)
MSR income (loss), net		0	0	0	0
Realized gains, net		0	0	0	0
Total noninterest income, net		0	(25)	(36)	(61)
Direct operating expenses		(9,994)	(9,789)	(19,554)	(18,894)
Benefit from income taxes		598	9	1,544	135
Net income		(18,894)	(16,032)	(36,940)	(31,171)
Corporate/Other
Segment Reporting Information [Line Items]
Interest income		6,469	6,414	13,494	13,245
Interest expense		(13,553)	(11,470)	(27,438)	(23,055)
Net Interest Income		(7,084)	(5,056)	(13,944)	(9,810)
Provision for loan losses		0	604	0	(23)
Mortgage banking and investment activities		(684)	(346)	(1,813)	(525)
MSR income (loss), net		0	0	0	0
Realized gains, net		0	71	0	176
Total noninterest income, net		(684)	(275)	(1,813)	(349)
Direct operating expenses		(9,994)	(9,831)	(19,554)	(18,988)
Benefit from income taxes		598	9	1,544	135
Net income		$ (17,164)	$ (14,549)	$ (33,767)	$ (29,035)

[1] For the three months ended June 30, 2015, there were no other-than-temporary impairments. For the three months ended June 30, 2014, other-than-temporary impairments were $2,915, of which $264 were recognized through the Income Statement and $2,651 were recognized in Accumulated Other Comprehensive Income.For the six months ended June 30, 2015, there were no other-then-temporary impairments. For the six months ended June 30, 2014, other-than-temporary impairments were $4,585, of which $377 were recognized through the Income Statement, and $4,208 were recognized in Accumulated Other Comprehensive Income.