Freestanding Derivative Financial Instruments - Schedule of Notional or Contractual Amounts and Fair Values of Derivative Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Derivative [Line Items]
Total derivative instruments, Assets, Fair Value	$ 79,257	$ 68,151
Fair Value, Derivative Assets, Cash Margin	0	14,664
Total derivative instruments, Liabilities, Fair Value	13,753	30,024
Fair Value, Derivative Liabilities, Cash Margin	30,032	2,780
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Notional/ Contractual Amount	3,746,480	2,825,924
Fair Value, Derivative Assets	50,750	60,400
Fair Value, Derivative Liabilities	4,791	263
Forward Sales Commitments [Member]
Derivative [Line Items]
Notional/ Contractual Amount	5,701,163	4,989,400
Fair Value, Derivative Assets	22,586	332
Fair Value, Derivative Liabilities	8,672	29,744
MBS Purchase Commitments [Member]
Derivative [Line Items]
Notional/ Contractual Amount	1,408,000	1,847,000
Fair Value, Derivative Assets	5,921	7,419
Fair Value, Derivative Liabilities	$ 290	$ 17