Activity in Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017	[1]
Valuation Allowance [Line Items]
Balance, beginning of period				$ 158,046	$ 158,290
Charge-offs				(12,848)	(17,736)
Recoveries				1,169	697
Balance, end of period	$ 160,652	$ 154,683	[1]	160,652	154,683
Non-Covered Loans
Valuation Allowance [Line Items]
Provision for (recovery of) non-covered loan losses	4,714	11,645		14,285	13,432
Mortgage Receivable
Valuation Allowance [Line Items]
Balance, beginning of period				128,275	125,416
Charge-offs				(5,444)	(90)
Recoveries				229	180
Balance, end of period	129,697	121,721	[1]	129,697	121,721
Mortgage Receivable | Non-Covered Loans
Valuation Allowance [Line Items]
Provision for (recovery of) non-covered loan losses				6,637	(3,785)
Other loans
Valuation Allowance [Line Items]
Balance, beginning of period				29,771	32,874
Charge-offs				(7,404)	(17,646)
Recoveries				940	517
Balance, end of period	$ 30,955	$ 32,962	[1]	30,955	32,962
Other loans | Non-Covered Loans
Valuation Allowance [Line Items]
Provision for (recovery of) non-covered loan losses				$ 7,648	$ 17,217

[1] Represents allowance for losses on non-covered loans, excluding PCI loans.