Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Assets [Abstract]
Cash and due from banks	$ 161,977	$ 161,020
Interest-earning deposits in financial institutions	357,541	235,466
Total cash and cash equivalents	519,518	396,486
Securities available-for-sale, at fair value	3,240,586	3,559,437
Federal Home Loan Bank stock, at cost	17,250	19,710
Total investment securities	3,257,836	3,579,147
Gross loans and leases	14,542,522	14,528,165
Deferred fees and costs		(49,911)
Allowance for loan and lease losses	130,361	115,111
Total loans and leases, net	14,353,156	14,363,143
Equipment leased to others under operating leases	205,163	197,452
Premises and equipment, net	39,713	39,197
Foreclosed assets, net	18,310	22,120
Goodwill	2,175,791	2,176,291
Core deposit and customer relationship intangibles, net	48,137	53,220
Deferred tax asset, net	91,126	126,389
Other assets	322,259	335,045
Total assets	21,031,009	21,288,490
Liabilities and Equity [Abstract]
Noninterest-bearing deposits	6,139,963	6,171,455
Interest-bearing deposits	9,301,412	9,494,727
Total deposits	15,441,375	15,666,182
Borrowings	551,401	621,914
Subordinated debentures	438,723	436,000
Accrued interest payable and other liabilities	142,918	166,703
Total liabilities	16,574,417	16,890,799
Commitments and contingencies (Note 8)	0	0
Preferred stock ($0.01 par value; 5,000,000 shares authorized; none issued and outstanding)	0	0
Additional paid-in capital	4,353,706	4,405,775
Retained earnings	104,363	13,907
Common stock ($0.01 par value, 200,000,000 shares authorized at March 31, 2016 and December 31, 2015; 123,153,983 and 122,791,729 shares issued, respectively, including 1,562,557 and 1,211,951 shares of unvested restricted stock, respectively)	1,232	1,228
Treasury stock, at cost (1,382,731 and 1,378,002 shares at March 31, 2016 and December 31, 2015)	(51,188)	(51,047)
Accumulated other comprehensive income, net	48,479	27,828
Total stockholders' equity	4,456,592	4,397,691
Total liabilities and stockholders' equity	$ 21,031,009	$ 21,288,490