Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Current assets:
Allowance for uncollectible accounts	$ 4,067	$ 4,527
Shareholders' equity:
Common stock, no par value
Common stock, shares authorized	240,000,000	240,000,000
Common stock, shares issued	105,530,000	105,592,000