Holding Company Condensed Financial Information - Summary of Condensed Balance Sheets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash and cash equivalents	$ 101,385	$ 102,952	$ 223,017	$ 188,073
Total assets	1,145,456	1,203,152
Other liabilities	8,027	11,077
Shareholders' equity	98,380	103,482	113,899	75,015
Total liabilities and shareholders' equity	1,145,456	1,203,152
Holding Company [Member]
Cash and cash equivalents	128	959
Investment in subsidiary	98,275	102,602
Total assets	98,403	103,561
Other liabilities	23	79
Shareholders' equity	98,380	103,482
Total liabilities and shareholders' equity	$ 98,403	$ 103,561