Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Assets [Abstract]
Cash and due from banks	$ 140,873		$ 164,757
Interest-earning deposits in financial institutions	250,981		148,469
Total cash and cash equivalents	391,854		313,226
Securities available-for-sale, at fair value	1,595,409		1,567,177
Federal Home Loan Bank stock, at cost	28,905		40,609
Total investment securities	1,624,314		1,607,786
Gross loans and leases	12,302,292		11,904,684
Deferred fees and costs	(30,126)		(22,252)
Allowance for loan and lease losses	(92,378)		(84,455)
Total loans and leases, net	12,179,788		11,797,977
Equipment leased to others under operating leases	119,959		122,506
Premises and equipment, net	36,022		36,551
Foreclosed assets, net	35,940		43,721
Goodwill	1,728,380	[1]	1,720,479
Core deposit and customer relationship intangibles, net	15,703		17,204
Deferred tax asset, net	236,065		284,411
Other assets	275,915		290,744
Total assets	16,643,940		16,234,605
Liabilities and Equity [Abstract]
Noninterest-bearing deposits	3,029,463		2,931,352
Interest-bearing deposits	8,904,712		8,823,776
Total deposits	11,934,175		11,755,128
Borrowings	618,156		383,402
Subordinated debentures	431,448		433,583
Accrued interest payable and other liabilities	126,800		156,262
Total liabilities	13,110,579		12,728,375
Commitments and Contingencies	0		0
Preferred stock ($0.01 par value; 5,000,000 shares authorized; none issued and outstanding)	0		0
Common stock ($0.01 par value, 200,000,000 shares authorized at March 31, 2015 and December 31, 2014; 104,241,437 and 104,219,197 shares issued, respectively, including 1,129,445 and 1,108,505 shares of unvested restricted stock, respectively)	1,042		1,042
Additional paid-in capital	3,758,855		3,807,167
Accumulated deficit	(212,633)		(285,712)
Treasury stock, at cost (1,197,180 shares at March 31, 2015 and December 31, 2014)	(42,647)		(42,647)
Accumulated other comprehensive income, net	28,744		26,380
Total stockholders' equity	3,533,361		3,506,230
Total liabilities and stockholders' equity	16,643,940		16,234,605
Purchased Credit Impaired Loans and Leases [Member]
Assets [Abstract]
Deferred fees and costs	$ (61)		$ (61)

[1] The increase in goodwill for the Community Banking segment and National Lending segment compared to March 31, 2014, was due primarily to $1.5 billion from the CapitalSource Inc. merger.