Bank segment (HEI only) - Investment Securities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Amortized Cost
Due in one year or less	$ 5,000
Due after one year through five years	87,404
Due after five years through ten years	80,161
Due after ten years	28,753
Total amortized cost	201,318
Mortgage-related securities-FNMA, FHLMC and GNMA - amortized cost	1,220,304
Total available-for-sale securities, amortized cost	1,421,622	$ 1,118,350
Mortgage-related securities-FNMA, FHLMC and GNMA, amortized cost basis	44,515
Held-to-maturity Securities	44,515	0
Fair value
Due in one year or less	4,992
Due after one year through five years	87,020
Due after five years through ten years	79,358
Due after ten years	28,355
Total fair value	199,725
Mortgage-related securities-FNMA, FHLMC and GNMA - fair value	1,201,473
Estimated fair value	1,401,198	1,105,182
Mortgage-related securities - FNMA, FHLMC and GNMA, Fair Value	44,412
Held-to-maturity securities, Fair Value	44,412
Gains (losses) from sales of available-for-sale investments
Proceeds	0	16,423	$ 0
Interest income from taxable and non-taxable investment securities
Taxable	28,398	19,166	15,120
Non-taxable	425	18	0
Total	28,823	19,184	15,120
Available-for-sale securities pledged at carrying value	411,400	277,100
Available-for-sale securities, pledged at carrying value as collateral for securities sold under agreements to repurchase	165,100	114,900
FHLB Des Moines
Interest income from taxable and non-taxable investment securities
Cost method investments	9,700	11,200
Mortgage-related securities - FNMA, FHLMC and GNMA
Gains (losses) from sales of available-for-sale investments
Proceeds	0	16,400	0
Gross gains	0	600	0
Gross losses	$ 0	$ 0	$ 0