Premises and Equipment (Narrative) (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Depreciation		$ 41,000	$ 37,200	$ 36,300
Operating lease, right-of-use asset, amortization		27,600
Operating leases, rent expense, net		42,100	31,100	30,500
Short term operating lease rent expense		4,600
Non-operating lease components rent expense		9,900
Operating lease, payments		27,500
Recognition of right of use asset related to the new corporate headquarters facility	$ 121,700
Recognition of operating lease liability related to the new corporate headquarters facility	$ 121,700
Current period amortization of deferred gain		1,400	2,800	2,900
Partnership Interest [Member]
Property, Plant and Equipment [Line Items]
Operating leases, rent expense, net		$ 5,900	$ 464	$ 1,400