Stockholders' Equity (Details) (USD $)	0 Months Ended	1 Months Ended	3 Months Ended			0 Months Ended
	Dec. 06, 2012	May 31, 2011	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	May 02, 2013 Subsequent Event [Member]
Class of Stock [Line Items]
Cash dividend per common share	$ 0.19					$ 0.19
Dividend declared and paid, common shares			$ 0	$ 2,200,000	$ 2,000,000
Stock repurchase program, authorized amount		30,000,000.0
Common stock repurchased under repurchase program, shares			72,107		17,800
Common stock repurchased, average price per share			$ 48.96		$ 39.50
Common stock repurchased, amount			3,500,000		700,000
Common stock available for future share repurchases, amount			$ 2,300,000