Stockholders' Equity and Earnings per Share - Preferred Stock (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2025 USD ($) $ / shares shares	Dec. 31, 2024 USD ($)
Class of Stock [Line Items]
Total Outstanding Balance	$ 14,109,000	$ 14,109,000
Preferred Stock
Class of Stock [Line Items]
Shares Authorized | shares	464,170,000
Shares Outstanding | shares	464,170,000
Total Par Value	$ 464,170
Total Outstanding Balance	$ 14,109,000
Class 1 - 1996 Variable-rate
Class of Stock [Line Items]
Shares Authorized | shares	5,000,000.00
Shares Outstanding | shares	5,000,000.00
Total Par Value	$ 5,000
Redemption Price Per Share | $ / shares	$ 50.00
Total Outstanding Balance	$ 250,000
OTCQB Symbol	FMCCI
Preferred Stock, Dividend Payment Terms	Dividend rate resets quarterly and is equal to the sum of spread-adjusted three-month CME Term SOFR plus 1% divided by 1.377, and is capped at 9.00%.
Percentage added to benchmark rate in dividend rate reset calculation	1.00%
Denominator amount in dividend rate reset calculation	1.377
Class 1 - 1996 Variable-rate | Maximum
Class of Stock [Line Items]
Preferred stock, dividend rate	9.00%
Class 2 - 5.81%
Class of Stock [Line Items]
Preferred stock, dividend rate	5.81%
Shares Authorized | shares	3,000,000.00
Shares Outstanding | shares	3,000,000.00
Total Par Value	$ 3,000
Redemption Price Per Share | $ / shares	$ 50.00
Total Outstanding Balance	$ 150,000
Class 3 - 5%
Class of Stock [Line Items]
Preferred stock, dividend rate	5.00%
Shares Authorized | shares	8,000,000.00
Shares Outstanding | shares	8,000,000.00
Total Par Value	$ 8,000
Redemption Price Per Share | $ / shares	$ 50.00
Total Outstanding Balance	$ 400,000
OTCQB Symbol	FMCKK
Class 4 - 1998 Variable-rate
Class of Stock [Line Items]
Shares Authorized | shares	4,400,000
Shares Outstanding | shares	4,400,000
Total Par Value	$ 4,400
Redemption Price Per Share | $ / shares	$ 50.00
Total Outstanding Balance	$ 220,000
OTCQB Symbol	FMCCG
Preferred Stock, Dividend Payment Terms	Dividend rate resets quarterly and is equal to the sum of spread-adjusted three-month CME Term SOFR plus 1% divided by 1.377, and is capped at 7.50%.
Percentage added to benchmark rate in dividend rate reset calculation	1.00%
Denominator amount in dividend rate reset calculation	1.377
Class 4 - 1998 Variable-rate | Maximum
Class of Stock [Line Items]
Preferred stock, dividend rate	7.50%
Class 5 - 5.10%
Class of Stock [Line Items]
Preferred stock, dividend rate	5.10%
Shares Authorized | shares	8,000,000.00
Shares Outstanding | shares	8,000,000.00
Total Par Value	$ 8,000
Redemption Price Per Share | $ / shares	$ 50.00
Total Outstanding Balance	$ 400,000
OTCQB Symbol	FMCCH
Class 6 - 5.30%
Class of Stock [Line Items]
Preferred stock, dividend rate	5.30%
Shares Authorized | shares	4,000,000.00
Shares Outstanding | shares	4,000,000.00
Total Par Value	$ 4,000
Redemption Price Per Share | $ / shares	$ 50.00
Total Outstanding Balance	$ 200,000
Class 7 - 5.10%
Class of Stock [Line Items]
Preferred stock, dividend rate	5.10%
Shares Authorized | shares	3,000,000.00
Shares Outstanding | shares	3,000,000.00
Total Par Value	$ 3,000
Redemption Price Per Share | $ / shares	$ 50.00
Total Outstanding Balance	$ 150,000
Class 8 - 5.79%
Class of Stock [Line Items]
Preferred stock, dividend rate	5.79%
Shares Authorized | shares	5,000,000.00
Shares Outstanding | shares	5,000,000.00
Total Par Value	$ 5,000
Redemption Price Per Share | $ / shares	$ 50.00
Total Outstanding Balance	$ 250,000
OTCQB Symbol	FMCCK
Class 9 - 1999 Variable-rate
Class of Stock [Line Items]
Shares Authorized | shares	5,750,000
Shares Outstanding | shares	5,750,000
Total Par Value	$ 5,750
Redemption Price Per Share | $ / shares	$ 50.00
Total Outstanding Balance	$ 287,000
OTCQB Symbol	FMCCL
Preferred Stock, Dividend Payment Terms	Dividend rate resets on January 1 every five years after January 1, 2005 based on a five-year Constant Maturity Treasury rate, and is capped at 11.00%.
Preferred Stock, Redemption Terms	Optional redemption on December 31, 2004 and on December 31 every five years thereafter.
Preferred stock dividend rate reset period	5 years
Class 9 - 1999 Variable-rate | Maximum
Class of Stock [Line Items]
Preferred stock, dividend rate	11.00%
Class 10 - 2001 Variable-rate
Class of Stock [Line Items]
Shares Authorized | shares	6,500,000
Shares Outstanding | shares	6,500,000
Total Par Value	$ 6,500
Redemption Price Per Share | $ / shares	$ 50.00
Total Outstanding Balance	$ 325,000
OTCQB Symbol	FMCCM
Preferred Stock, Dividend Payment Terms	Dividend rate resets on April 1 every two years after April 1, 2003 based on the two-year Constant Maturity Treasury rate plus 0.10%, and is capped at 11.00%.
Preferred Stock, Redemption Terms	Optional redemption on March 31, 2003 and on March 31 every two years thereafter.
Percentage added to benchmark rate in dividend rate reset calculation	0.10%
Preferred stock dividend rate reset period	2 years
Class 10 - 2001 Variable-rate | Maximum
Class of Stock [Line Items]
Preferred stock, dividend rate	11.00%
Class 11 - 2001 Variable-rate
Class of Stock [Line Items]
Shares Authorized | shares	4,600,000
Shares Outstanding | shares	4,600,000
Total Par Value	$ 4,600
Redemption Price Per Share | $ / shares	$ 50.00
Total Outstanding Balance	$ 230,000
OTCQB Symbol	FMCCN
Preferred Stock, Dividend Payment Terms	Dividend rate resets on April 1 every year based on spread-adjusted 12-month CME Term SOFR minus 0.20%, and is capped at 11.00%.
Preferred Stock, Redemption Terms	Optional redemption on March 31, 2003 and on March 31 every year thereafter.
Percentage deducted from benchmark rate in dividend rate reset calculation	0.20%
Class 11 - 2001 Variable-rate | Maximum
Class of Stock [Line Items]
Preferred stock, dividend rate	11.00%
Class 12 - 5.81%
Class of Stock [Line Items]
Preferred stock, dividend rate	5.81%
Shares Authorized | shares	3,450,000
Shares Outstanding | shares	3,450,000
Total Par Value	$ 3,450
Redemption Price Per Share | $ / shares	$ 50.00
Total Outstanding Balance	$ 173,000
OTCQB Symbol	FMCCO
Class 13 - 6%
Class of Stock [Line Items]
Preferred stock, dividend rate	6.00%
Shares Authorized | shares	3,450,000
Shares Outstanding | shares	3,450,000
Total Par Value	$ 3,450
Redemption Price Per Share | $ / shares	$ 50.00
Total Outstanding Balance	$ 173,000
OTCQB Symbol	FMCCP
Class 14 - 2001 Variable-rate
Class of Stock [Line Items]
Preferred stock, dividend rate	11.00%
Shares Authorized | shares	4,020,000.00
Shares Outstanding | shares	4,020,000.00
Total Par Value	$ 4,020
Redemption Price Per Share | $ / shares	$ 50.00
Total Outstanding Balance	$ 201,000
OTCQB Symbol	FMCCJ
Preferred Stock, Dividend Payment Terms	Dividend rate resets on July 1 every two years after July 1, 2003 based on the two-year Constant Maturity Treasury rate plus 0.20%, and is capped at 11.00%.
Preferred Stock, Redemption Terms	Optional redemption on June 30, 2003 and on June 30 every two years thereafter.
Percentage added to benchmark rate in dividend rate reset calculation	0.20%
Preferred stock dividend rate reset period	2 years
Class 15 - 5.70%
Class of Stock [Line Items]
Preferred stock, dividend rate	5.70%
Shares Authorized | shares	6,000,000.00
Shares Outstanding | shares	6,000,000.00
Total Par Value	$ 6,000
Redemption Price Per Share | $ / shares	$ 50.00
Total Outstanding Balance	$ 300,000
OTCQB Symbol	FMCKP
Class 16 - 5.81%
Class of Stock [Line Items]
Preferred stock, dividend rate	5.81%
Shares Authorized | shares	6,000,000.00
Shares Outstanding | shares	6,000,000.00
Total Par Value	$ 6,000
Redemption Price Per Share | $ / shares	$ 50.00
Total Outstanding Balance	$ 300,000
Class 17 - 2006 Variable-rate
Class of Stock [Line Items]
Shares Authorized | shares	15,000,000.00
Shares Outstanding | shares	15,000,000.00
Total Par Value	$ 15,000
Redemption Price Per Share | $ / shares	$ 50.00
Total Outstanding Balance	$ 750,000
OTCQB Symbol	FMCCS
Preferred Stock, Dividend Payment Terms	Dividend rate resets quarterly and is equal to the sum of spread-adjusted three-month CME Term SOFR plus 0.50% but not less than 4.00%.
Percentage added to benchmark rate in dividend rate reset calculation	0.50%
Class 17 - 2006 Variable-rate | Minimum
Class of Stock [Line Items]
Preferred stock, dividend rate	4.00%
Class 18 - 6.42%
Class of Stock [Line Items]
Preferred stock, dividend rate	6.42%
Shares Authorized | shares	5,000,000.00
Shares Outstanding | shares	5,000,000.00
Total Par Value	$ 5,000
Redemption Price Per Share | $ / shares	$ 50.00
Total Outstanding Balance	$ 250,000
OTCQB Symbol	FMCCT
Class 19 - 5.90%
Class of Stock [Line Items]
Preferred stock, dividend rate	5.90%
Shares Authorized | shares	20,000,000.00
Shares Outstanding | shares	20,000,000.00
Total Par Value	$ 20,000
Redemption Price Per Share | $ / shares	$ 25.00
Total Outstanding Balance	$ 500,000
OTCQB Symbol	FMCKO
Class 20 - 5.57%
Class of Stock [Line Items]
Preferred stock, dividend rate	5.57%
Shares Authorized | shares	44,000,000.00
Shares Outstanding | shares	44,000,000.00
Total Par Value	$ 44,000
Redemption Price Per Share | $ / shares	$ 25.00
Total Outstanding Balance	$ 1,100,000
OTCQB Symbol	FMCKM
Class 21 - 5.66%
Class of Stock [Line Items]
Preferred stock, dividend rate	5.66%
Shares Authorized | shares	20,000,000.00
Shares Outstanding | shares	20,000,000.00
Total Par Value	$ 20,000
Redemption Price Per Share | $ / shares	$ 25.00
Total Outstanding Balance	$ 500,000
OTCQB Symbol	FMCKN
Class 22 - 6.02%
Class of Stock [Line Items]
Preferred stock, dividend rate	6.02%
Shares Authorized | shares	20,000,000.00
Shares Outstanding | shares	20,000,000.00
Total Par Value	$ 20,000
Redemption Price Per Share | $ / shares	$ 25.00
Total Outstanding Balance	$ 500,000
OTCQB Symbol	FMCKL
Class 23 - 6.55%
Class of Stock [Line Items]
Preferred stock, dividend rate	6.55%
Shares Authorized | shares	20,000,000.00
Shares Outstanding | shares	20,000,000.00
Total Par Value	$ 20,000
Redemption Price Per Share | $ / shares	$ 25.00
Total Outstanding Balance	$ 500,000
OTCQB Symbol	FMCKI
Class 24 - 2007 Fixed-to-floating rate
Class of Stock [Line Items]
Preferred stock, dividend rate	8.375%
Shares Authorized | shares	240,000,000.00
Shares Outstanding | shares	240,000,000.00
Total Par Value	$ 240,000
Redemption Price Per Share | $ / shares	$ 25.00
Total Outstanding Balance	$ 6,000,000
OTCQB Symbol	FMCKJ
Preferred Stock, Dividend Payment Terms	Dividend rate is set at an annual fixed rate of 8.375% from December 4, 2007 through December 31, 2012. For the period beginning on or after January 1, 2013, dividend rate resets quarterly and is equal to the higher of: (a) the sum of spread-adjusted three-month CME Term SOFR plus 4.16% per annum; or (b) 7.875% per annum.
Preferred Stock, Redemption Terms	Optional redemption on December 31, 2012 and on December 31 every five years thereafter.
Percentage added to benchmark rate in dividend rate reset calculation	4.16%
Class 24 - 2007 Fixed-to-floating rate | Maximum
Class of Stock [Line Items]
Preferred stock, dividend rate	7.875%