Loans and Leases (Details Textual) (USD $)	12 Months Ended	3 Months Ended		12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2013		Apr. 07, 2014
Financing Receivable, Impaired [Line Items]
Unfunded Commitments For Troubled Debt Restructurings	$ 214,000				$ 7,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	0				0
Loans held for investment, net	11,882,432,000				4,312,352,000
Loans and Leases Receivable, Gross	11,904,684,000				4,313,335,000
Financing Receivable Recorded Investment Thirty to Eighty Nine Days Past Due	8,700,000				4,200,000
Financing Receivable Recorded Investment Nonaccrual Status Current	56,100,000				37,300,000
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	7,500,000
NonCovered [Member]
Financing Receivable, Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	83,621,000
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	18,818,000				5,233,000
Loans held for investment, net	11,591,641,000				3,929,556,000	[1]
Loans and Leases Receivable, Gross	11,613,832,000				3,930,539,000
Financing Receivables, Impaired, Troubled Debt Restructuring, Write-down		129,000	1,600,000	921,000
Financing Receivable Recorded Investment Thirty to Eighty Nine Days Past Due	19,406,000				23,897,000
Non Purchased Credit Impaired Loans and Leases [Member] | Covered [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	61,500,000				85,900,000
Purchased Credit Impaired Loans and Leases [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	290,791,000				382,796,000	[1]
Purchased Credit Impaired Loans and Leases [Member] | Covered [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	100,400,000				362,500,000
Nonperforming Financing Receivable [Member] | NonCovered [Member]
Financing Receivable, Impaired [Line Items]
Loans and Leases Receivable, Gross					46,774,000
Nonperforming Financing Receivable [Member] | NonCovered [Member] | Commercial Real Estate Construction Financing Receivable [Member]
Financing Receivable, Impaired [Line Items]
Loans held for investment, net	1,178,000				2,830,000
Capitalsource, Inc. [Member] | NonCovered [Member]
Financing Receivable, Impaired [Line Items]
Business Combination, Acquired Receivables, Fair Value							6,800,000,000
Business Combination, Acquired Receivables, Gross Contractual Amount							9,400,000,000
Undiscounted Cash Flows Not Expected to be collected							839,800,000
Capitalsource, Inc. [Member] | Covered [Member]
Financing Receivable, Impaired [Line Items]
Business Combination, Acquired Receivables, Fair Value							$ 79,200,000

[1] (1)As of December 31, 2013, the amounts of loans covered by loss sharing provisions of FDIC loss sharing agreements in the Non-PCI and PCI categories were $85.9 million and $362.5 million.