Fair Value - Fair Value Measurement (Detail) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assumed Gain/(Loss) From Loan Sale	$ 7,876
Interest Rate Movement Effect	10,462
Servicing Rights Value	14,159
Security Price Change	(6,635)
Total Fair Value Measurement Gain/(Loss)	25,862		$ 14,309
Mortgage Banking [Member] | Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rate Lock Commitments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional or Principal Amount	878,701
Assumed Gain/(Loss) From Loan Sale	4,796
Interest Rate Movement Effect	5,231
Servicing Rights Value	8,925
Total Fair Value Measurement Gain/(Loss)	18,952
Mortgage Banking [Member] | Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Forward Sales Contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional or Principal Amount	1,169,844
Security Price Change	(6,635)
Total Fair Value Measurement Gain/(Loss)	(6,635)
Mortgage Banking [Member] | Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Mortgages Held for Sale [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional or Principal Amount	449,148		$ 447,444
Assumed Gain/(Loss) From Loan Sale	3,080
Interest Rate Movement Effect	5,231
Servicing Rights Value	5,234
Total Fair Value Measurement Gain/(Loss)	$ 13,545	$ 10,880