Freestanding Derivative Financial Instruments - Schedule of Notional or Contractual Amounts and Fair Values of Derivative Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Derivative Assets	$ 87,937	$ 58,512
Derivative Liabilities	11,804	6,475
Derivative Assets, Cash Margin	0	209
Derivative Liabilities, Cash Margin	30,941	10,101
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Notional/ Contractual Amount	3,046,549	3,398,892
Derivative Assets	53,394	51,519
Derivative Liabilities	4,193	1,070
Forward Sales Commitments [Member]
Derivative [Line Items]
Notional/ Contractual Amount	3,978,000	4,650,000
Derivative Assets	29,471	6,427
Derivative Liabilities	7,609	4,871
MBS Purchase Commitments [Member]
Derivative [Line Items]
Notional/ Contractual Amount	623,500	703,000
Derivative Assets	5,072	566
Derivative Liabilities	$ 2	$ 534