Borrowings - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Feb. 27, 2014
Schedule Of Borrowings [Line Items]
Junior subordinated debentures	$ 834,000,000
Debt Maturity, Start Year	Jan. 01, 2027
Debt Maturity, End Year	Dec. 31, 2033
Interest rate of debt instrument			8.50%
Agreements to repurchase securities	1,400,000,000	1,400,000,000
Collateral posted	1,600,000,000	1,600,000,000
Trust Preferred Securities Subject to Mandatory Redemption [Member]
Schedule Of Borrowings [Line Items]
Junior subordinated debentures			$ 350,000,000
2015 [Member]
Schedule Of Borrowings [Line Items]
Trust preferred capital securities	25.00%
2016 [Member]
Schedule Of Borrowings [Line Items]
Trust preferred capital securities	0.00%