Shareholders' Equity: (Details) (USD $)	0 Months Ended	3 Months Ended
	Jan. 23, 2013	Mar. 30, 2013 Common Stock Repurchase Program
Dividends
Cash dividend approved by Board of Directors (in dollars per share)	$ 0.04
Repurchase of Common Stock
Number of shares repurchased		4,756
Aggregate purchase price of shares repurchased		$ 269,600
Aggregate purchase price per share of shares repurchased (in dollars per share)		$ 56.69
Number of additional shares that can be repurchased		356,396