Fair Value - Fair Value Measurement (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assumed Gain/(Loss) From Loan Sale	$ 2,627
Interest Rate Movement Effect	8,267
Servicing Rights Value	13,472
Security Price Change	(10,057)
Total Fair Value Measurement Gain/(Loss)	14,309	$ 5,824
Mortgage Banking: | Level 2 | Fair Value, Measurements, Recurring | Rate lock commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional or Principal Amount	682,152
Assumed Gain/(Loss) From Loan Sale	1,360
Interest Rate Movement Effect	4,630
Servicing Rights Value	7,496
Security Price Change	0
Total Fair Value Measurement Gain/(Loss)	13,486
Mortgage Banking: | Level 2 | Fair Value, Measurements, Recurring | Forward sales contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional or Principal Amount	1,089,923
Assumed Gain/(Loss) From Loan Sale	0
Interest Rate Movement Effect	0
Servicing Rights Value	0
Security Price Change	(10,057)
Total Fair Value Measurement Gain/(Loss)	(10,057)
Mortgage Banking: | Level 2 | Fair Value, Measurements, Recurring | Mortgages held for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional or Principal Amount	447,444	350,558
Assumed Gain/(Loss) From Loan Sale	1,267
Interest Rate Movement Effect	3,637
Servicing Rights Value	5,976
Security Price Change	0
Total Fair Value Measurement Gain/(Loss)	$ 10,880	$ (1,931)