Mortgage Servicing Rights - Details of Retention and Purchase of MSRs (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Mortgage Servicing Rights [Line Items]
MSRs recognized			$ 36,834	$ 11,976
Mortgage servicing rights
Mortgage Servicing Rights [Line Items]
MSRs recognized	$ 32,463	$ 11,807	51,217	$ 14,666
Associated Principal	2,997,971		4,906,964
Mortgage servicing rights | Jumbo MSR Additions
Mortgage Servicing Rights [Line Items]
MSRs recognized	6,174		8,138
Associated Principal	623,524		861,521
Mortgage servicing rights | Jumbo MSR Additions | Securitization
Mortgage Servicing Rights [Line Items]
MSRs recognized	6,002		7,874
Associated Principal	607,402		835,254
Mortgage servicing rights | Jumbo MSR Additions | Loan Sales
Mortgage Servicing Rights [Line Items]
MSRs recognized	172		264
Associated Principal	16,122		26,267
Mortgage servicing rights | Conforming MSR Additions
Mortgage Servicing Rights [Line Items]
MSRs recognized	26,289		43,079
Associated Principal	2,374,447		4,045,443
Mortgage servicing rights | Conforming MSR Additions | Loan Sales
Mortgage Servicing Rights [Line Items]
MSRs recognized	14,990		28,701
Associated Principal	1,348,871		2,701,529
Mortgage servicing rights | Conforming MSR Additions | From purchases
Mortgage Servicing Rights [Line Items]
MSRs recognized	11,299		14,378
Associated Principal	$ 1,025,576		$ 1,343,914