Income Taxes (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred income tax assets
Net operating loss carryforwards	$ 167,072	$ 308,617
Allowance for loan losses	100,419	103,884
Tax credit carryforwards	67,031	59,434
Employee benefits and deferred compensation	21,024	21,177
Net unrealized losses on investment securities available for sale	19,413	3,072
Non-performing loan interest	19,137	16,604
Deferred revenue	18,639	16,529
Other	19,759	18,573
Total gross deferred tax assets	432,494	547,890
Less valuation allowance	(9,658)	(11,713)
Total deferred tax assets	422,836	536,177
Deferred tax liabilities
Fixed assets held for sale	(8,179)	(5,985)
Purchase accounting adjustments	(5,765)	(811)
Excess tax over financial statement depreciation	(5,343)	(8,564)
Ownership interest in partnerships	(5,242)	(4,537)
Other	(2,951)	(4,332)
Total gross deferred tax liabilities	(27,480)	(24,229)
Net deferred tax asset	$ 395,356	$ 511,948