Fair Value Measurements - Schedule of Fair Value of Derivative Instruments and Loans Held for Sale (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Derivative notional amount and balance sheet location
Assumed Gain on Sale	$ 20,173	$ 29,575
Interest Rate Movement Effect	(872)
Total Fair Value Adjustment	19,301	29,575
Derivative assets	16,130	11,678
Derivative Liabilities	(7,563)	(1,333)
Fair Value Adjustment To Loans Held for Sale	10,734	19,231
Loans Held for Sale
Derivative notional amount and balance sheet location
Notional or Principal Amount	537,093	2,479,880
Assumed Gain on Sale	8,353	20,108
Interest Rate Movement Effect	2,381	(877)
Total Fair Value Adjustment	10,734	19,231
Fair Value Adjustment To Loans Held for Sale	10,734	19,231
Rate Lock Commitments
Derivative notional amount and balance sheet location
Notional or Principal Amount	427,870	267,710
Assumed Gain on Sale	11,820	9,467
Interest Rate Movement Effect	3,859	(1,494)
Total Fair Value Adjustment	15,679	7,973
Derivative assets	15,679	7,973
Forward Sale Contracts
Derivative notional amount and balance sheet location
Notional or Principal Amount	889,485	2,747,590
Interest Rate Movement Effect	(6,101)	2,371
Total Fair Value Adjustment	(6,101)	2,371
Derivative assets	451	3,705
Derivative Liabilities	(6,552)	$ (1,333)
Interest Rate Swaps
Derivative notional amount and balance sheet location
Notional or Principal Amount	26,100
Interest Rate Movement Effect	(1,011)
Total Fair Value Adjustment	(1,011)
Derivative Liabilities	$ (1,011)