Debt (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014 DebentureRepurchased	Sep. 30, 2013 DebentureRepurchased	Sep. 30, 2014 DebentureRepurchased	Sep. 30, 2013 DebentureRepurchased	Dec. 31, 2013
Long-term debt [Abstract]
Carrying Value	$ 111,941,000	$ 117,347,000	$ 111,941,000	$ 117,347,000	$ 111,911,000
Fair Value Level 2	120,975,000	127,349,000	120,975,000	127,349,000	122,319,000
Loss on extinguishment of debt			(84,000)	(137,000)
5.5% Senior notes [Member]
Long-term debt [Abstract]
Debt maturity date	May 15, 2013
Stated interest rate (in hundredths)	5.50%	5.50%	5.50%	5.50%	5.50%
Debt maturity period	10 years
Face value of debt	100,000,000		100,000,000
5.875% Senior notes [Member]
Long-term debt [Abstract]
Carrying Value	100,000,000	100,000,000	100,000,000	100,000,000	100,000,000
Debt maturity date	Jun. 01, 2021
Stated interest rate (in hundredths)	5.875%	5.875%	5.875%	5.875%	5.875%
Debt maturity period	10 years
Face value of debt	100,000,000		100,000,000
Percentage principal amount to offered to repurchase notes (in hundredths)	101.00%
5.875% Senior notes [Member] | Level 2 [Member]
Long-term debt [Abstract]
Fair Value Level 2	108,200,000	108,000,000	108,200,000	108,000,000	108,500,000
0% Subordinated debentures [Member]
Long-term debt [Abstract]
Carrying Value	11,941,000	17,347,000	11,941,000	17,347,000	11,911,000
Debt maturity date	Dec. 31, 2015
Stated interest rate (in hundredths)	0.00%	0.00%	0.00%	0.00%	0.00%
Effective interest rate (in hundredths)	7.45%	7.45%	7.45%	7.45%	7.45%
Debentures repurchased (face value)	103,200	0	716,200	1,200,000
Debentures repurchased (loss in dollars)	10,000	0	84,000	137,000
Debt maturity period	5 years
Face value of debt	86,400,000		86,400,000
Dividends declared related to issuance of debt (in dollars per share)	$ 3.20
Par value of debentures	100,000,000		100,000,000
Debt redemption price as percentage of principal amount (in hundredths)	100.00%		100.00%
Number of debentures repurchased	1,032	0	7,165	11,974
Maximum amount of debt and equity to be issued under Shelf Registration	500,000,000		500,000,000
Amount available for debt and equity issuance under Shelf Registration	400,000,000		400,000,000
0% Subordinated debentures [Member] | Level 2 [Member]
Long-term debt [Abstract]
Fair Value Level 2	$ 12,775,000	$ 19,349,000	$ 12,775,000	$ 19,349,000	$ 13,819,000