Balance Sheet Offsetting (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Offsetting Liabilities
Gross Amounts Recognized	$ 188,113	$ 206,911
Gross Amounts Offset	0	0
Net Amounts Presented	188,113	206,911
Gross Amounts Not Offset, Financial Instruments	(5,853)	(5,268)
Gross Amounts Not Offset, Cash Collateral	(167,270)	(201,643)
Net Amount	14,990	0
Collateral posted with counterparties	50,700	52,400
Repurchase Agreements
Offsetting Repurchase Agreement Liabilities
Gross Amounts Recognized	165,000	165,000
Gross Amounts Offset	0	0
Net Amounts Presented	165,000	165,000
Gross Amounts Not Offset, Financial Instruments	0	0
Gross Amounts Not Offset, Cash Collateral	(165,000)	(165,000)
Net Amount	0	0
Interest Rate Caps and Swaps
Offsetting Assets
Gross Amounts Recognized	25,405	26,087
Gross Amounts Offset	0	0
Net Amounts Presented	25,405	26,087
Gross Amounts Not Offset, Financial Instruments	(5,853)	(5,268)
Gross Amounts Not Offset, Cash Collateral	0	0
Net Amount	19,552	20,819
Offsetting Derivative Liabilities
Gross Amounts Recognized	23,113	41,911
Gross Amounts Offset	0	0
Net Amounts Presented	23,113	41,911
Gross Amounts Not Offset, Financial Instruments	(5,853)	(5,268)
Gross Amounts Not Offset, Cash Collateral	(2,270)	(36,643)
Net Amount	$ 14,990	$ 0