Income Taxes (Schedule of Deferred Income Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred Tax Assets, Gross [Abstract]
Allowance for credit losses	$ 40,069	$ 35,760
Employee benefits	50,868	51,584
Real Estate Mortgage Investment Credit	3,791	4,831
Acquired liabilities	5,931	6,296
Acquired loans	25,388	51,701
Available for sale securities	11,475	3,862
Loan fees and expenses	0	0
Federal NOL carryforwards	102,194	131,195
Alternative minimum tax credit carryforward	112,861	83,428
General business tax credit carryforward	2,924	1,982
State income tax (net of federal benefit)	2,441	1,970
Other	1,789	467
Total deferred tax assets	359,731	373,076
Deferred tax liabilities:
Leased assets and depreciation	(41,649)	(24,699)
FHLB stock	(18,641)	(18,165)
Loan fees and expenses	(1,480)	(2,537)
Goodwill	(26,885)	(16,580)
Core deposit intangibles	(18,697)	(22,013)
Other	0	0
Total deferred tax liabilities	(107,352)	(83,994)
Total net deferred tax asset	$ 252,379	$ 289,082