Fair Value - Fair Value Measurement (Detail) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assumed Gain/(Loss) From Loan Sale	$ 3,588
Interest Rate Movement Effect	2,037
Servicing Rights Value	12,894
Security Price Change	(1,368)
Total Fair Value Measurement Gain/(Loss)	17,151		$ 14,309
Mortgage Banking [Member] | Level 2 [Member] | Fair Value, Recurring [Member] | Rate Lock Commitments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability	827,120
Assumed Gain/(Loss) From Loan Sale	2,071
Interest Rate Movement Effect	1,239
Servicing Rights Value	8,158
Total Fair Value Measurement Gain/(Loss)	11,468
Mortgage Banking [Member] | Level 2 [Member] | Fair Value, Recurring [Member] | Forward Sales Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Disclosure, Off-balance Sheet Risks, Face Amount, Liability	1,101,965
Security Price Change	(1,368)
Total Fair Value Measurement Gain/(Loss)	(1,368)
Mortgage Banking [Member] | Level 2 [Member] | Fair Value, Recurring [Member] | Mortgages Held for Sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assumed Gain/(Loss) From Loan Sale	1,517
Interest Rate Movement Effect	798
Servicing Rights Value	4,736
Fair Value, Option, Changes in Fair Value, Gain (Loss)	7,051	$ 10,880
Fair Value, Principal Amount, Loans Held for Sale	$ 404,172		$ 447,444