Acquisitions (Textual) (Details) (USD $)				0 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 07, 2012 Independent Bank [Member] Branches	Dec. 07, 2012 Independent Bank [Member] Core Deposits [Member]	Mar. 31, 2013 OAK [Member]	Dec. 31, 2012 OAK [Member]	Mar. 31, 2012 OAK [Member]	Apr. 30, 2010 OAK [Member] Offices	Dec. 07, 2012 Branch Offices [Member] Independent Bank [Member]
Business Acquisition [Line Items]
Number of branches acquired (branches)				21
Deposits acquired				$ 404,000,000
Loans acquired				44,000,000					627,000,000
Acquisition purchase price									83,700,000	8,100,000
Premium paid on deposits purchased				11,500,000
Premium paid as a percentage of deposits purchased (percent)				2.85%
Discount on loans purchased (percent)				1.75%
Goodwill	120,164,000	120,164,000	113,414,000	6,800,000
Intangibles acquired					5,600,000
Service provided by acquiree bank through number of branches									14
Assets of acquiree company									820,000,000
Deposits of acquiree company									693,000,000
Brokered deposits of acquiree company									193,000,000
Contractually required principal and interest payments of loan portfolio									683,000,000
Contractually required interest payments of loan portfolio									97,000,000
Expected principal cash flows of contractually required acquired loan portfolio									636,000,000
Expected interest cash flows of contractually required acquired loan portfolio									88,000,000
Expected interest cash flows of contractually required loan portfolio fair value									627,000,000
Nonaccretable difference									56,000,000
Expected credit losses									47,000,000
Outstanding contractual principal balance of acquired loan portfolio						400,000,000	419,000,000	508,000,000
Carrying amount of acquired loan portfolio						$ 374,000,000	$ 393,000,000	$ 473,000,000