Compensation Plans: Stock Based (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2024 USD ($) shares $ / shares	Dec. 31, 2023 USD ($) shares $ / shares	Dec. 31, 2022 USD ($) shares $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant	1,900,000
Impact outright issuance of one share has on number of available shares	1
Performance Shares (PSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum impact of issuance of one performance share award on available shares under the equity incentive plan	2
Multiplier applied to PSU awards at settlement			2.0
Award vesting period	3 years
Stock-based compensation expense | $	$ 5.5	$ 2.8	$ 2.6
Unrecognized stock based compensation expense | $	13.9
Fair value of PSUs/RSUs granted in period | $	$ 9.9	$ 7.7	$ 7.4
Non-vested at beginning of year (in shares)	469,432	273,258	464,483
Non-vested outstanding at beginning of year grant date fair value ($/share) | $ / shares	$ 27.83	$ 26.67	$ 12.80
Granted (in shares)	231,120	256,633	276,010
Granted grant date fair value ($/share) | $ / shares	$ 42.76	$ 29.93	$ 26.67
Vested (in shares)	0	(15,950)	(461,387)
Vested grant date fair value ($/share) | $ / shares	$ 0	$ 25.50	$ 12.81
Forfeited (in shares)	(6,186)	(44,509)	(5,848)
Forfeited grant date fair value ($/share) | $ / shares	$ 25.87	$ 26.45	$ 18.24
Non-vested at end of year (in shares)	694,366	469,432	273,258
Non-vested outstanding at end of year grant date fair value ($/share) | $ / shares	$ 32.99	$ 27.83	$ 26.67
Multiplier assumed	1	1	1
Shares held for settlement of income and payroll tax obligations (in shares)			349,487
Shares Issued in Period	0	0	654,923
Fair value of PSUs/RSUs Vested in Period | $			$ 12.3
Performance Shares (PSUs) | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Multiplier applied to PSU awards at settlement	0
Performance Shares (PSUs) | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Multiplier applied to PSU awards at settlement	2
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense | $	$ 16.7	$ 14.8	13.5
Unrecognized stock based compensation expense | $	29.7
Fair value of PSUs/RSUs granted in period | $	$ 21.9	$ 20.2	$ 18.0
Non-vested at beginning of year (in shares)	1,080,544	1,375,052	1,841,237
Non-vested outstanding at beginning of year grant date fair value ($/share) | $ / shares	$ 31.49	$ 22.42	$ 13.79
Granted (in shares)	504,010	630,474	526,776
Granted grant date fair value ($/share) | $ / shares	$ 43.44	$ 32.03	$ 34.08
Vested (in shares)	(507,171)	(805,205)	(920,927)
Vested grant date fair value ($/share) | $ / shares	$ 30.18	$ 16.75	$ 12.17
Forfeited (in shares)	(37,546)	(119,777)	(72,034)
Forfeited grant date fair value ($/share) | $ / shares	$ 32.96	$ 29.26	$ 18.24
Non-vested at end of year (in shares)	1,039,837	1,080,544	1,375,052
Non-vested outstanding at end of year grant date fair value ($/share) | $ / shares	$ 37.87	$ 31.49	$ 22.42
Restricted stock units, shares settled gross of shares for tax withholdings	508,927	803,449	920,927
Shares held for settlement of income and payroll tax obligations (in shares)	158,252	249,233	284,423
Shares Issued in Period	350,675	554,216	636,504
Number of Shares Represented by Each RSU	1
Fair value of PSUs/RSUs Vested in Period | $	$ 15.3	$ 13.5	$ 11.2
Retirement vesting Increment	6 months
Retirement increment vesting period	6 months