Basis of Presentation and Accounting Policies - Carrying Amount and Estimated Fair Value of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Financial assets:
Loans, net	$ 2,502,625	$ 2,447,455	$ 1,960,478
Financial liabilities:
Deposits	3,011,383	3,000,061	2,491,282
Other borrowings	59,677	194,572
Carrying Amount [Member]
Financial assets:
Loans, net	2,482,601	2,435,067	1,930,095
Financial liabilities:
Deposits	3,010,647	2,999,231	2,489,973
Other borrowings	59,677	194,572
Level 1 [Member]
Financial assets:
Loans, net
Financial liabilities:
Deposits
Other borrowings
Level 2 [Member]
Financial assets:
Loans, net	1,651,409	1,565,919	1,458,604
Financial liabilities:
Deposits	3,011,383	3,000,061	2,491,282
Other borrowings	59,677	194,572
Level 3 [Member]
Financial assets:
Loans, net	$ 851,216	$ 881,536	$ 501,874