Acquisitions (Textual) (Details) (USD $)				0 Months Ended		0 Months Ended				0 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 07, 2012 Independent Bank [Member] Branches	Dec. 07, 2012 Independent Bank [Member] Core Deposits [Member]	Apr. 30, 2010 OAK [Member] Offices	Sep. 30, 2013 OAK [Member]	Dec. 31, 2012 OAK [Member]	Sep. 30, 2012 OAK [Member]	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
Certain Loans Acquired in Transfer, Accretable Yield						97,000,000
Outstanding contractual principal balance of acquired loan portfolio							334,000,000	419,000,000	440,000,000
Carrying amount of acquired loan portfolio							$ 309,000,000	$ 393,000,000	$ 413,000,000