Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Net income	$ 44,291,000	$ 36,732,000	$ 132,338,000	$ 97,998,000
Other comprehensive income
Change in unrealized gain (loss) on securities available for sale	3,144,000	20,905,000	(56,148,000)	27,699,000
Tax effect and reclassification adjustment	(1,151,000)	(7,570,000)	20,206,000	(10,060,000)
Unrealized holding gains (losses) arising during period	1,993,000	13,335,000	(35,942,000)	17,639,000
Non-credit related unrealized gain on other-than-temporarily impaired debt securities	237,000	136,000	378,000	1,877,000
Tax effect	(87,000)	(50,000)	(139,000)	(688,000)
Reclassification adjustment for gains (losses) included in net income	150,000	86,000	239,000	1,189,000
Change in unrealized gain (loss) on cash flow hedges	1,309,000	(2,614,000)	15,795,000	(6,389,000)
Tax effect	(478,000)	955,000	(5,765,000)	2,250,000
Change in unrealized loss on cash flow hedges	831,000	(1,659,000)	10,030,000	(4,139,000)
Adjustment to postretirement benefit obligations	0	0	(26,000)	0
Tax effect	0	0	9,000	0
Adjustment to postretirement benefit obligations, net of tax	0	0	(17,000)	0
Total other comprehensive income (loss)	2,974,000	11,762,000	(25,690,000)	14,689,000
Total comprehensive income	$ 47,265,000	$ 48,494,000	$ 106,648,000	$ 112,687,000