Changes in Fair Value of Loans Held for Sale (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Fair Value, Option, Quantitative Disclosures [Line Items]
Mortgage Banking Income	[1]	$ 727	$ (21,432)	$ (54,468)	$ (24,378)
Loans held for sale
Fair Value, Option, Quantitative Disclosures [Line Items]
Mortgage Banking Income	[1]	9,644	6,328	28,687	10,714
Mortgage servicing rights
Fair Value, Option, Quantitative Disclosures [Line Items]
Mortgage Banking Income	[1]	$ (8,917)	$ (27,760)	$ (83,155)	$ (35,092)

[1] Does not include the effect of hedging activities, which is included in "Other non-interest income."