Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues
Revenues	$ 2,380,654	$ 2,602,982	$ 3,239,542
Expenses
Total expenses	2,032,479	2,280,429	2,906,942
Operating income (loss)
Operating income	348,175	322,553	332,600
Merger termination fee	90,000	0	0
Interest expense, net – other than on deposit liabilities and other bank borrowings	(75,803)	(77,150)	(76,352)
Allowance for borrowed funds used during construction	3,144	2,457	2,579
Allowance for equity funds used during construction	8,325	6,928	6,771
Income before income taxes	373,841	254,788	265,598
Income taxes	123,695	93,021	95,579
Net income	250,146	161,767	170,019
Preferred stock dividends of subsidiaries	1,890	1,890	1,890
Net income for common stock	$ 248,256	$ 159,877	$ 168,129
Basic earnings per common share (in dollars per share)	$ 2.30	$ 1.50	$ 1.65
Diluted earnings per common share (in dollars per share)	2.29	1.50	1.63
Dividends per common share (in dollars per share)	$ 1.24	$ 1.24	$ 1.24
Weighted-average number of common shares outstanding (in shares)	108,102	106,418	101,968
Net effect of potentially dilutive shares (in shares)	207	303	969
Adjusted weighted-average shares (in shares)	108,309	106,721	102,937
Electric utility
Revenues
Revenues	$ 2,094,368	$ 2,335,166	$ 2,987,323
Expenses
Total expenses	1,809,900	2,061,050	2,711,555
Operating income (loss)
Operating income	284,468	274,116	275,768
Income before income taxes	229,113	217,131	220,361
Income taxes	84,801	79,422	80,725
Net income	144,312	137,709	139,636
Preferred stock dividends of subsidiaries	1,995	1,995	1,995
Net income for common stock	142,317	135,714	137,641
Bank
Revenues
Revenues	285,924	267,733	252,497
Expenses
Total expenses	198,572	183,921	173,202
Operating income (loss)
Operating income	87,352	83,812	79,295
Income before income taxes	87,352	83,812	79,295
Income taxes	30,073	29,082	27,994
Net income	57,279	54,730	51,301
Preferred stock dividends of subsidiaries	0	0	0
Net income for common stock	57,279	54,730	51,301
Other
Revenues
Revenues	362	83	(278)
Expenses
Total expenses	24,007	35,458	22,185
Operating income (loss)
Operating income	(23,645)	(35,375)	(22,463)
Income before income taxes	57,376	(46,155)	(34,058)
Income taxes	8,821	(15,483)	(13,140)
Net income	48,555	(30,672)	(20,918)
Preferred stock dividends of subsidiaries	(105)	(105)	(105)
Net income for common stock	$ 48,660	$ (30,567)	$ (20,813)