Goodwill and Other Intangible Assets (Details) (USD $)			3 Months Ended			1 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Mar. 31, 2013 Plains Capital	Sep. 30, 2013 Plains Capital	Nov. 30, 2012 Plains Capital	Sep. 30, 2013 Bank FNB Core deposits
Goodwill and Other Intangible Assets
Carrying amount of goodwill	$ 251,808,000	$ 253,770,000			$ 230,100,000
Adjustments related to PlainsCapital acquisition			2,000,000
Purchase price allocation adjustments amount expected				0
Other intangible assets	75,942,000	77,738,000
Estimated fair value of indefinite lived intangible assets related to state licenses acquired as a part of the NLASCO acquisition	3,000,000
Intangible asset recorded in connection with acquisition						$ 6,400,000
Amortization period						7 years