Summary of Significant Accounting and Reporting Policies (Schedule of Earnings Per Share, Basic And Diluted) (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Numerators:
Numerator for both basic and diluted EPS, net income	$ 69,881,000	$ 55,521,000	$ 52,097,000	$ 45,431,000	$ 39,599,000	$ 41,877,000	$ 40,767,000	$ 46,345,000	$ 222,929,949	$ 168,586,840	$ 164,668,228
Denominators:
Denominator for basic EPS, weighted-average common shares outstanding									143,460,018	143,097,530	142,492,699
Potentially dilutive shares resulting from stock option plans									814,153	870,501	1,784,109
Denominator for diluted EPS									144,274,171	143,968,031	144,276,808