Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Net income	$ 43,494,000	$ 45,648,000	$ 80,656,000	$ 88,047,000
Other comprehensive income (loss):
Change in unrealized gain (loss) on securities available for sale	11,241,000	(53,120,000)	27,362,000	(59,291,000)
Tax effect and reclassification adjustment	(4,040,000)	19,177,000	(9,847,000)	21,356,000
Unrealized holding gains (losses) arising during period	7,201,000	(33,943,000)	17,515,000	(37,935,000)
Non-credit related unrealized gain on other-than-temporarily impaired debt securities	0	433,000	0	141,000
Tax effect	0	(159,000)	0	(52,000)
Reclassification adjustment for gains included in net income	0	274,000	0	89,000
Change in unrealized gain on cash flow hedges	3,473,000	10,081,000	7,573,000	14,486,000
Tax effect	(1,267,000)	(3,679,000)	(2,764,000)	(5,287,000)
Change in unrealized gain on cash flow hedges	2,206,000	6,402,000	4,809,000	9,199,000
Changes in postretirement benefit obligations	0	0	0	(26,000)
Tax effect	0	0	0	9,000
Changes in postretirement benefit obligations, net of tax	0	0	0	(17,000)
Total other comprehensive income (loss)	9,407,000	(27,267,000)	22,324,000	(28,664,000)
Total comprehensive income	$ 52,901,000	$ 18,381,000	$ 102,980,000	$ 59,383,000