Acquisitions (Details) (USD $)	3 Months Ended	9 Months Ended		0 Months Ended		3 Months Ended	9 Months Ended	0 Months Ended			0 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Nov. 30, 2012 Plains Capital	Oct. 15, 2013 Bank FNB item	Sep. 13, 2013 Bank FNB item	Sep. 30, 2013 Bank FNB	Sep. 30, 2013 Bank FNB	Sep. 13, 2013 Bank FNB Maximum	Sep. 13, 2013 Bank FNB Fair value adjustments	Sep. 13, 2013 Bank FNB Covered loans	Sep. 13, 2013 Bank FNB Covered loans Commercial	Sep. 13, 2013 Bank FNB Covered loans Single family residential loans	Sep. 13, 2013 Bank FNB Non-covered loans
Acquisitions
Percentage of losses to be absorbed by FDIC on the first $240.4 million of losses incurred as per the loss sharing agreement					80.00%
Threshold amount of losses incurred for 80% of losses to be absorbed by FDIC as per the loss sharing agreement, first layer					$ 240,400,000
Percentage of losses to be absorbed by FDIC in excess of $240.4 million up to and including $365.7 million of losses incurred as per the loss sharing agreement					0.00%
Threshold amount of losses incurred for 0% of losses to be absorbed by FDIC as per the loss sharing agreement, second layer								365,700,000
Percentage of losses to be absorbed by FDIC in excess of $365.7 million of losses incurred as per the loss sharing agreement					80.00%
Period of loss-sharing agreements in effect											5 years	10 years
Period of loss recovery provisions in effect											8 years	10 years
Period for which payment is required to be made to the FDIC of true-up amount					10 years
Pre-tax bargain purchase gain	3,271,000	3,271,000			3,271,000				3,271,000
Transaction-related expenses						200,000	200,000
Net assets received from the FDIC and the estimated fair value adjustments resulting in the bargain purchase gain
Cost basis net assets					182,169,000
Cash payment received from the FDIC					45,000,000
Securities			730,800,000		286,214,000				(3,341,000)
Loans			3,200,000,000						(337,572,000)	1,105,421,000			45,915,000
Premises and equipment					71,806,000				(1,358,000)
Other real estate owned									(69,456,000)	120,985,000
FDIC indemnification asset					189,773,000				189,773,000
Other intangible assets			70,700,000		6,380,000				6,380,000
Deposits	2,200,000,000	2,200,000,000	4,500,000,000		2,211,740,000				(8,282,000)
Other					13,887,000				(42,000)
Bargain purchase gain	3,271,000	3,271,000			3,271,000				3,271,000
Number of premises purchased from the FDIC					44
Aggregate purchase price of premises purchased from the FDIC				3,800,000	59,500,000
Period of option from the acquisition date, to purchase real estate from the FDIC					30 days
Number of additional premises purchased pursuant to exercise of option from the FDIC				5
Period of exclusive option to purchase real estate not listed in bid form, from the FDIC					90 days
Period of option from the acquisition date, to lease real estate and purchase furniture and equipment from the FDIC					90 days
Exercise of right to purchase furniture and equipment					9,800,000
Fair values of the identifiable assets acquired, and liabilities assumed
Cash and due from banks					362,695,000
Securities			730,800,000		286,214,000				(3,341,000)
Loans			3,200,000,000						(337,572,000)	1,105,421,000			45,915,000
Premises and equipment					71,806,000				(1,358,000)
FDIC indemnification asset					189,773,000				189,773,000
Other real estate owned									(69,456,000)	120,985,000
Other assets					39,709,000
Other intangible assets			70,700,000		6,380,000				6,380,000
Total identifiable assets acquired			6,500,000,000		2,228,898,000
Deposits	2,200,000,000	2,200,000,000	4,500,000,000		2,211,740,000				(8,282,000)
Other liabilities					13,887,000				(42,000)
Total liabilities assumed			5,900,000,000		2,225,627,000
Net identifiable assets acquired/ bargain purchase gain					$ 3,271,000