Investment Securities (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Investment securities
Available-for-sale securities, Cost	$ 169,000,000		$ 178,800,000
Available-for-sale securities, Gross Unrealized Gain	1,500,000		1,700,000
Available-for-sale securities, Gross Unrealized (Loss) excluding OTTI			(100,000)
Available-for-sale securities, Fair Value	170,500,000		180,400,000
Cost method investments, Cost	12,900,000		13,400,000
Cost method investments, Fair Value	12,900,000		13,400,000
Totals, Cost	181,900,000		192,200,000
Totals, Fair Value	183,400,000		193,800,000
Additional information regarding available-for-sale securities
Proceeds from sales	21,500,000	29,700,000
Gross realized gains included in earnings as a result of sales	1,000,000	500,000
Net unrealized gains included in OCI, net of tax	800,000	2,400,000
Net gains reclassified out of OCI into earnings, net of tax	1,000,000	300,000
Maturity information for the investments in debt securities
Due within one year	136,500,000
Due after one year through five years	15,200,000
Due after 10 years	17,600,000
Total debt securities	169,300,000
Amount of cost method assets for which fair value estimation deemed impracticable	7,600,000
Student loan auction rate securities
Investment securities
Available-for-sale securities, Cost	17,100,000		37,600,000
Available-for-sale securities, Gross Unrealized Gain	400,000		1,200,000
Available-for-sale securities, Fair Value	17,500,000		38,800,000
Corporate bonds
Investment securities
Available-for-sale securities, Cost	11,500,000		6,600,000
Available-for-sale securities, Fair Value	11,500,000		6,600,000
State and municipal obligations
Investment securities
Available-for-sale securities, Cost	140,300,000		134,500,000
Available-for-sale securities, Gross Unrealized (Loss) excluding OTTI			(100,000)
Available-for-sale securities, Fair Value	140,300,000		134,400,000
Securities in a continuous unrealized loss position with unrealized losses presented by length of time
Less than 12 months, Fair Value			45,300,000
More than 12 months, Fair Value			100,000
Total Fair Value			45,400,000
Total Unrealized Losses			(100,000)
State and municipal obligations | Maximum
Securities in a continuous unrealized loss position with unrealized losses presented by length of time
Less than 12 months, Unrealized Losses			50,000
More than 12 months, Unrealized Losses			50,000
Preferred stock
Investment securities
Available-for-sale securities, Cost	100,000		100,000
Available-for-sale securities, Gross Unrealized Gain	1,100,000		500,000
Available-for-sale securities, Fair Value	$ 1,200,000		$ 600,000