Basis of Presentation and Accounting Policies - Carrying Amount and Estimated Fair Value of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Financial assets:
Loans, net	$ 2,022,693	$ 1,966,592	$ 1,989,786
Financial liabilities:
Deposits	2,444,244	2,624,883	2,581,465
Carrying Amount [Member]
Financial assets:
Loans, net	1,983,062	1,934,754	1,960,195
Financial liabilities:
Deposits	2,443,421	2,624,663	2,580,117
Level 1 [Member]
Financial assets:
Loans, net
Financial liabilities:
Deposits
Level 2 [Member]
Financial assets:
Loans, net	1,561,480	1,406,366	1,393,115
Financial liabilities:
Deposits	2,444,244	2,624,883	2,581,465
Level 3 [Member]
Financial assets:
Loans, net	$ 461,213	$ 560,226	$ 596,671