Note Guarantees (Changes in the Corporation's liability of estimated losses from credit recourses agreements) (Detail) - Financial Guarantee - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Guarantor Obligations
Balance as of beginning of period	$ 56,230	$ 58,820
Provision (reversal) for recourse liability	(311)	3,000
Net charge-offs	(3,908)	(4,395)
Balance as of end of period	$ 52,011	$ 57,425