Condensed Financial Information of Parent Company (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Assets [Abstract]
Other assets, net	$ 44,673	$ 40,086
TOTAL ASSETS	6,482,915	6,436,691	6,739,769
Liabilities	5,768,101	5,792,836
Stockholders' equity	714,814	643,855	638,228	614,892
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	6,482,915	6,436,691
Parent Company [Member]
Assets [Abstract]
Investment in subsidiaries	808,358	752,324
Other assets, net	31,428	22,185
TOTAL ASSETS	839,786	774,509
Liabilities	124,972	130,654
Stockholders' equity	714,814	643,855
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	$ 839,786	$ 774,509