Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Net income	$ 37,162,000	$ 42,399,000
Other comprehensive income (loss):
Change in unrealized gain (loss) on securities available for sale	16,121,000	(6,171,000)
Tax effect and reclassification adjustment	(5,807,000)	2,179,000
Unrealized holding gains (losses) arising during period	10,314,000	(3,992,000)
Non-credit related unrealized loss on other-than-temporarily impaired debt securities	0	(292,000)
Tax effect	0	107,000
Reclassification adjustment for losses included in net income	0	(185,000)
Change in unrealized gain on cash flow hedges	4,100,000	4,405,000
Tax effect	(1,497,000)	(1,608,000)
Change in unrealized gain on cash flow hedges	2,603,000	2,797,000
Changes in postretirement benefit obligations	0	(26,000)
Tax effect	0	9,000
Changes in postretirement benefit obligations, net of tax	0	(17,000)
Total other comprehensive income (loss)	12,917,000	(1,397,000)
Total comprehensive income	$ 50,079,000	$ 41,002,000