Subsequent Events (Details) (USD $) In Thousands, except Share data, unless otherwise specified	0 Months Ended	3 Months Ended				180 Months Ended		3 Months Ended	0 Months Ended	3 Months Ended		0 Months Ended
	Aug. 06, 2013	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2014	Feb. 05, 2013	Mar. 31, 2014 Restricted Stock [Member]	May 07, 2014 Subsequent Event [Member]	Mar. 31, 2013 Quarterly Dividend [Member]	Mar. 31, 2012 Quarterly Dividend [Member]	Aug. 06, 2013 Quarterly Dividend [Member] Subsequent Event [Member]
Subsequent Event [Line Items]
Stock repurchased (in shares)									38,895
Average price per share of repurchased shares (in dollars per share)		$ 79.59		$ 53.57		$ 42.76			$ 76.06
Shares available to be repurchased (in shares)							500,000
Shares authorized for issuance (in shares)		1,500,000				1,500,000
Dividends declared (in dollars per share)		$ 0.06		$ 0.05						$ 0.06	$ 0.05	$ 0.06
Dividends declared date												May 06, 2014
Dividends payable date				Mar. 25, 2014	Mar. 26, 2013							Jun. 24, 2014
Dividends record date				Mar. 11, 2014	Mar. 12, 2013							Jun. 10, 2014
Expected expense related to Shareholder-designated charitable contribution program		$ 0	$ 5,300	$ 5,000
RSAs granted (in shares)	431,700							2,100
Restricted stock award shares approved grant date fair value (in dollars per share)	$ 57.86							$ 81.99
Percentage stock based compensation expense recognize over three years vesting period (in hundredths)		30.00%						60.00%
Stock based compensation expense recognize over five years vesting period		70.00%						40.00%
Vesting period for recognition of 30 percent of stock based compensation expense		3 years
Vesting period for recognition of 70 percent of stock based compensation expense		5 years