Fair Value - Fair Value Measurement (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assumed Gain/(Loss) From Loan Sale	$ 2,283
Interest Rate Movement Effect	2,059
Servicing Rights Value	14,980
Security Price Change	(3,899)
Total Fair Value Measurement Gain/(Loss)	15,423	$ 5,824
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	857,052
Assumed Gain/(Loss) From Loan Sale	1,402
Interest Rate Movement Effect	1,683
Servicing Rights Value	9,689
Total Fair Value Measurement Gain/(Loss)	12,774
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	1,168,371
Security Price Change	(3,899)
Total Fair Value Measurement Gain/(Loss)	(3,899)
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	393,258	350,558
Assumed Gain/(Loss) From Loan Sale	881
Interest Rate Movement Effect	376
Servicing Rights Value	5,291
Total Fair Value Measurement Gain/(Loss)	$ 6,548	$ 1,931