Off-Balance Sheet Arrangements, Guarantees and Other Commitments - Summary Information Related to Commitments to Extend Credit (Excluding Letters of Credit) (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Disclosure Off Balance Sheet Arrangements Guarantees And Other Commitments Additional Information [Abstract]
Fixed interest rate commitments	$ 1,394,063	$ 1,392,781
Variable interest rate commitments	11,070,302	9,101,973
Total loan commitments available for funding	12,464,365	10,494,754
Commercial and standby letters of credit	1,105,617	975,968
Total unfunded credit commitments	13,569,982	11,470,722
Commitments unavailable for funding	1,267,797	1,006,168
Maximum lending limits for accounts receivable factoring arrangements	978,752	894,276
Reserve for unfunded credit commitments	$ 33,319	$ 29,983