Fair Value Measurements - Schedule of Fair Value of Derivative Instruments and Loans Held for Sale (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Derivative notional amount and balance sheet location
Assumed Gain on Sale	$ 59,109	$ 29,575
Interest Rate Movement Effect	(348)
Total Fair Value Adjustment	58,761	29,575
Derivative assets	33,796	11,678
Derivative Liabilities	(2,918)	(1,333)
Fair Value Adjustment To Loans Held for Sale	27,883	19,231
Loans Held for Sale
Derivative notional amount and balance sheet location
Notional or Principal Amount	1,271,145	2,479,880
Assumed Gain on Sale	28,649	20,108
Interest Rate Movement Effect	(766)	(877)
Total Fair Value Adjustment	27,883	19,231
Fair Value Adjustment To Loans Held for Sale	27,883	19,231
Rate Lock Commitments
Derivative notional amount and balance sheet location
Notional or Principal Amount	862,987	267,710
Assumed Gain on Sale	30,460	9,467
Interest Rate Movement Effect	(76)	(1,494)
Total Fair Value Adjustment	30,384	7,973
Derivative assets	30,411	7,973
Derivative Liabilities	(27)
Forward Sale Contracts
Derivative notional amount and balance sheet location
Notional or Principal Amount	2,111,142	2,747,590
Interest Rate Movement Effect	772	2,371
Total Fair Value Adjustment	772	2,371
Derivative assets	3,385	3,705
Derivative Liabilities	(2,613)	$ (1,333)
Interest Rate Swaps
Derivative notional amount and balance sheet location
Notional or Principal Amount	10,310
Interest Rate Movement Effect	(278)
Total Fair Value Adjustment	(278)
Derivative Liabilities	$ (278)