Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Consolidated Statements of Comprehensive Income
Net income	$ 183,682	$ 230,178	$ 213,780
Other comprehensive (loss) income, net of tax:
Net unrealized gains (losses) on pensions and other benefits	4,291	(3,354)	8,986
Net unrealized losses on investment securities	(14,159)	(34,852)	(9,573)
Net unrealized gains on cash flow derivative hedges	1,496	1,454	785
Other comprehensive (loss) income	(8,372)	(36,752)	198
Total comprehensive income	$ 175,310	$ 193,426	$ 213,978