Stock-based Compensation (Details) (USD $)	6 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		0 Months Ended						6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Stock option awards	Mar. 31, 2013 Stock option awards	Jun. 30, 2013 Restricted stock units	Jun. 30, 2012 Restricted stock units	Jun. 30, 2013 Restricted stock units	Jun. 30, 2012 Restricted stock units	Mar. 26, 2013 Restricted stock units Members of management	Mar. 26, 2013 Restricted stock units Members of management Requisite service period of one year	Mar. 26, 2013 Restricted stock units Members of management Requisite service period of two years	Mar. 26, 2013 Restricted stock units Members of management Requisite service period of three years	Mar. 26, 2013 Restricted stock units Members of management Minimum	Mar. 26, 2013 Restricted stock units Members of management Maximum	Jun. 30, 2013 DSUs Directors
Stock-based Compensation
Shares authorized for repurchase under stock repurchase plan	895,655
Number of shares held in treasury	1,589,100	1,616,282
Shares
Outstanding at beginning of year (in shares)				857,468
Forfeited (in shares)			156,439
Outstanding at end of period (in shares)			701,029	857,468
Exercisable at end of period (in shares)			701,029
Weighted-Average Exercise Price
Outstanding at beginning of year (in dollars per share)				$ 17.01
Forfeited (in dollars per share)			$ 16.00
Outstanding at end of period (in dollars per share)			$ 17.24	$ 17.01
Exercisable at end of period (in dollars per share)			$ 17.24
Weighted-Average Remaining Contractual Term
Outstanding at end of period			2 years 6 months 25 days
Exercisable at end of period			2 years 6 months 25 days
Shares
Non-vested at beginning of year (in shares)	769,403						736,412								32,991
Granted (in shares)	13,158						13,158		13,158
Dividend Equivalents Earned (in shares)	5,296						4,806								490
Vested (in shares)	(54,393)						(20,912)								(33,481)
Forfeited (in shares)	(20,014)						(20,014)
Non-vested at end of period (in shares)	713,450				713,450		713,450			4,386	4,386	4,386
Outstanding at end of period (in shares)	770,860				713,450		713,450								57,410
Weighted-Average Grant Date Fair Value
Non-vested at beginning of year (in dollars per share)	$ 4.92
Granted (in dollars per share)	$ 4.56
Dividend Equivalents Earned (in dollars per share)	$ 4.25
Vested (in dollars per share)	$ 4.92
Forfeited (in dollars per share)	$ 5.23
Non-vested at end of period (in dollars per share)	$ 4.90
Outstanding at end of period (in dollars per share)	$ 4.90
Additional disclosures
Stock price (in dollars per share)									$ 4.56
Amount of compensation cost to be recognized					$ 1,800,000		$ 1,800,000		$ 60,000
Requisite service period										1 year	2 years	3 years
Vesting rights of shares granted (as a percent)									100.00%
Period over which cost will be recognized							2 years 7 months 6 days						1 year	3 years
Compensation expense recognized					$ 100,000	$ 200,000	$ 400,000	$ 400,000