Stock-Based Compensation (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Fair value assumptions of stock options
Dividend yield	2.00%	2.00%
Risk-free interest rate	0.99%	1.20%
Weighted average expected volatility	34.35%	48.94%
Weighted average expected life	6 years	6 years
Weighted average per share fair value of stock options	$ 3.80	$ 5.03
Summary of Company's Stock Option Activities
Stock Options Shares Outstanding, Beginning balance	8,640,558	7,055,274
Granted, Shares	1,020,979	3,060,519
Exercised, Shares	(110,793)	(11,120)
Forfeited or expired, Shares	(397,741)	(1,464,115)
Stock Options Shares Outstanding, Ending balance	9,153,003	8,640,558
Options exercisable, shares	5,770,664	4,603,963
Stock Options Outstanding, Weighted Average Exercise Price, Beginning balance	$ 18.88	$ 21.99
Granted, Weighted Average Exercise Price	$ 14.02	$ 12.97
Exercised, Weighted Average Exercise Price	$ 13.41	$ 13.16
Forfeited or expired, Weighted Average Exercise Price	$ 21.19	$ 21.56
Stock Options Outstanding, Weighted Average Exercise Price, Ending balance	$ 18.30	$ 18.88
Options Exercisable, Weighted Average Exercise Price	$ 21.14	$ 23.80
Stock Options Outstanding, Weighted Average Remaining Contractual Term	6 years 9 months	6 years 5 months
Options exercisable, Weighted Average Remaining Contractual Term	5 years 4 months	4 years 4 months
Stock Options Outstanding, Aggregate Intrinsic Value	$ 10,458	$ 570
Options exercisable, Aggregate Intrinsic Value	$ 4,598	$ 43