Freestanding Derivative Financial Instruments - Schedule of Notional or Contractual Amounts and Fair Values of Derivative Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Total derivative instruments, Assets, Fair Value	$ 68,151	$ 62,365
Fair Value, Derivative Assets, Cash Margin	14,664	0
Total derivative instruments, Liabilities, Fair Value	30,024	5,882
Fair Value, Derivative Liabilities, Cash Margin	2,780	19,148
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Notional/ Contractual Amount	2,825,924	2,202,638
Fair Value, Derivative Assets	60,400	42,831
Fair Value, Derivative Liabilities	263	3,755
Forward Sales Commitments [Member]
Derivative [Line Items]
Notional/ Contractual Amount	4,989,400	2,903,700
Fair Value, Derivative Assets	332	19,534
Fair Value, Derivative Liabilities	29,744	247
MBS Purchase Commitments [Member]
Derivative [Line Items]
Notional/ Contractual Amount	1,847,000	308,700
Fair Value, Derivative Assets	7,419	0
Fair Value, Derivative Liabilities	$ 17	$ 1,880