Derivatives - Schedule of Derivative Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Jul. 31, 2017
Derivatives Fair Value [Line Items]
Notional amount			$ 100,000
Not Designated As Hedging
Derivatives Fair Value [Line Items]
Notional amount	$ 2,053,274	$ 1,810,484
Asset	13,867	8,258
Liability	3,655	1,699
Not Designated As Hedging | Interest rate contracts
Derivatives Fair Value [Line Items]
Notional amount	175,726	146,754
Asset	2,360	1,146
Liability	2,360	1,146
Not Designated As Hedging | Forward commitments
Derivatives Fair Value [Line Items]
Notional amount	919,571	870,574
Liability	1,295	553
Not Designated As Hedging | Interest rate-lock commitments
Derivatives Fair Value [Line Items]
Notional amount	692,977	504,156
Asset	10,179	6,768
Not Designated As Hedging | Futures Contracts
Derivatives Fair Value [Line Items]
Notional amount	243,000	283,000
Asset	1,180	315
Not Designated As Hedging | Option Contracts
Derivatives Fair Value [Line Items]
Notional amount	22,000	6,000
Asset	148	29
Designated as Hedging
Derivatives Fair Value [Line Items]
Notional amount	30,000	130,000
Asset	1,037	1,432
Designated as Hedging | Interest Rate Swaps
Derivatives Fair Value [Line Items]
Notional amount	30,000	130,000
Asset	$ 1,037	$ 1,432