Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017		Jun. 30, 2016
Consolidated Statements of Comprehensive Income [Abstract]
Net income	$ 52,267	$ 46,907	$ 101,281		$ 50,746
Other comprehensive income:
Net change in unrealized gain on securities available for sale and hedges	12,661	16,629	13,845		45,601
Reclassification of net losses realized and included in earnings	1,718	711	3,105		1,802
Valuation adjustment for pension plan amendment	17,315		17,315	[1]
Other valuation adjustments for employee benefit plan	(10,782)		(10,782)
Amortization of unrealized net loss on securities transferred to HTM	1,099	830	1,749		1,628
Other comprehensive income before income taxes	22,011	18,170	25,232		49,031
Income tax expense	7,938	6,645	9,139		17,977
Other comprehensive income net of income taxes	14,073	11,525	16,093		31,054
Comprehensive income	$ 66,340	$ 58,432	$ 117,374		$ 81,800

[1] For further discussion on the pension plan amendment, see Note 11 - Retirement Plans.