Loans, Changes in the Allowance for Loan Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Changes in the allowance for loan losses
Balance at beginning of year	$ 266,302	$ 268,315	$ 297,409
Provision for loan losses	38,000	13,000	10,000
Charge offs	(52,280)	(44,096)	(88,061)
Recoveries	22,242	29,083	48,967
Net charge offs	(30,038)	(15,013)	(39,094)
Balance at end of year	274,264	266,302	268,315
Change in the allowance for unfunded commitments
Allowance for Credit Losses	298,664	291,202	290,215
Reserve for Off-balance Sheet Activities [Member]
Change in the allowance for unfunded commitments
Balance at beginning of year	24,900	21,900	21,800
Provision for unfunded commitments	(500)	3,000	100
Balance at end of year	$ 24,400	$ 24,900	$ 21,900