Financial Instruments with Off-Balance-Sheet Risk - Schedule of Financial Instruments Outstanding Contract Amounts Represent Credit Risk (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value Disclosures [Abstract]
Commitments to fund loans	$ 231,294	$ 202,809
Unfunded commitments to fund mortgage warehouse loans	713,619	905,442
Unfunded commitments under lines of credit	430,995	177,457
Letters of credit	36,206	29,116
Other unused commitments	$ 7,685	$ 8,010