Securities (Detail) - Credit-Related CDO Impairment Losses (USD $) In Thousands, unless otherwise specified	12 Months Ended			72 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Securities [Line Items]
Credit-Related CDO Impairment Losses	$ 0	$ 2,226	$ 936	$ 38,665
No 1
Securities [Line Items]
Credit-Related CDO Impairment Losses	0	0	0	10,360
No 2
Securities [Line Items]
Credit-Related CDO Impairment Losses	0	1,534	525	9,402
No 3
Securities [Line Items]
Credit-Related CDO Impairment Losses	0	692	411	2,262
No 4
Securities [Line Items]
Credit-Related CDO Impairment Losses	0	0	0	1,078
No 5
Securities [Line Items]
Credit-Related CDO Impairment Losses	0	0	0	8,570
No 6
Securities [Line Items]
Credit-Related CDO Impairment Losses	0	0	0	243
No 7
Securities [Line Items]
Credit-Related CDO Impairment Losses	$ 0	$ 0	$ 0	$ 6,750