Freestanding Derivative Financial Instruments - Schedule of Notional or Contractual Amounts and Fair Values of Derivative Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Derivative Assets	$ 40,522	$ 87,937
Derivative Liabilities	5,924	11,804
Cash Margin, Paid	865	0
Cash Margin, Received	2,387	30,941
Interest Rate Lock Commitments
Derivative [Line Items]
Notional/ Contractual Amount	2,215,331	3,046,549
Derivative Assets	31,687	53,394
Derivative Liabilities	2,175	4,193
Forward Sales Commitments
Derivative [Line Items]
Notional/ Contractual Amount	3,083,723	3,978,000
Derivative Assets	8,835	29,471
Derivative Liabilities	1,462	7,609
MBS Purchase Commitments
Derivative [Line Items]
Notional/ Contractual Amount	699,000	623,500
Derivative Assets	0	5,072
Derivative Liabilities	$ 2,287	$ 2