Stockholders' Equity (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended						161 Months Ended					3 Months Ended																								6 Months Ended			3 Months Ended				6 Months Ended					3 Months Ended				6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jun. 30, 2012	Jan. 03, 2012	May 06, 2011	Feb. 09, 2011	Jan. 15, 2011	Mar. 31, 2016 Q1 [Member]	Mar. 31, 2015 Q1 [Member]	Mar. 31, 2014 Q1 [Member]	Mar. 31, 2013 Q1 [Member]	Mar. 31, 2012 Q1 [Member]	Mar. 31, 2011 Q1 [Member]	Jun. 30, 2016 Q2 [Member]	Jun. 30, 2015 Q2 [Member]	Jun. 30, 2014 Q2 [Member]	Jun. 30, 2013 Q2 [Member]	Jun. 30, 2012 Q2 [Member]	Jun. 30, 2011 Q2 [Member]	Sep. 30, 2016 Q3 [Member]	Sep. 30, 2015 Q3 [Member]	Sep. 30, 2014 Q3 [Member]	Sep. 30, 2013 Q3 [Member]	Sep. 30, 2012 Q3 [Member]	Sep. 30, 2011 Q3 [Member]	Dec. 31, 2016 Q4 [Member]	Dec. 31, 2015 Q4 [Member]	Dec. 31, 2014 Q4 [Member]	Dec. 31, 2013 Q4 [Member]	Dec. 31, 2012 Q4 [Member]	Dec. 31, 2011 Q4 [Member]	Jun. 30, 2012 Class A [Member]	Dec. 31, 2011 Class A [Member]	Jun. 30, 2011 Class A [Member]	Jun. 30, 2012 Class A [Member] Quarterly Dividend [Member]	Mar. 31, 2012 Class A [Member] Quarterly Dividend [Member]	Jun. 30, 2011 Class A [Member] Quarterly Dividend [Member]	Mar. 31, 2011 Class A [Member] Quarterly Dividend [Member]	Jun. 30, 2012 Class A [Member] Quarterly Dividend [Member]	Jun. 30, 2011 Class A [Member] Quarterly Dividend [Member]	Jun. 30, 2012 Class B [Member]	Dec. 31, 2011 Class B [Member]	Jun. 30, 2011 Class B [Member]	Jun. 30, 2012 Class B [Member] Quarterly Dividend [Member]	Mar. 31, 2012 Class B [Member] Quarterly Dividend [Member]	Jun. 30, 2011 Class B [Member] Quarterly Dividend [Member]	Mar. 31, 2011 Class B [Member] Quarterly Dividend [Member]	Jun. 30, 2012 Class B [Member] Quarterly Dividend [Member]	Jun. 30, 2011 Class B [Member] Quarterly Dividend [Member]
Stockholders' Equity [Abstract]
Shares outstanding (in shares)																																								6,609,863	6,684,149	6,647,212							20,020,730	20,070,746	20,142,640
Dividends Payable [Line Items]
Dividends declared (in dollars per share)	$ 0.29	$ 0.04	$ 0.33	$ 0.07																																							$ 0.29	$ 0.04	$ 0.04	$ 0.03	$ 0.63	$ 0.07				$ 0.29	$ 0.04	$ 0.04	$ 0.03	$ 0.63	$ 0.07
Dividend declared date																																															Aug. 07, 2012									Aug. 07, 2012
Dividend payment date																																											Jun. 26, 2012	Mar. 27, 2012	Jun. 28, 2011	Mar. 29, 2011	Sep. 25, 2012					Jun. 26, 2012	Mar. 27, 2012	Jun. 28, 2011	Mar. 29, 2011	Sep. 25, 2012
Dividend record date																																											Jun. 12, 2012	Mar. 13, 2012	Jun. 14, 2011	Mar. 15, 2011	Sep. 11, 2012					Jun. 12, 2012	Mar. 13, 2012	Jun. 14, 2011	Mar. 15, 2011	Sep. 11, 2012
Voting Rights [Abstract]
Number of votes per share																																								1									10
Stock Award and Incentive Plan [Abstract]
Number of incentive plans			2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares reserved for issuance under each plan, maximum (in shares)	1,500,000		1,500,000								1,500,000
Term of nonqualified stock options, maximum (in years)			10 years
Percentage options granted under plans vest after three years (in hundredths)			75.00%
Percentage options granted under plan vest after four years (in hundredths)			100.00%
Vesting period for 75 percent of stock options (in years)			three
Vesting period for 100 percent of stock options (in years)			four
Restricted stock award shares approved grant date fair value (in dollars per share)												$ 43.49		$ 45.77	$ 48.85
RSA shares outstanding (in shares)	373,500	289,800	373,500	289,800						275,600	373,500
Percentage stock based compensation expense recognize over three years vesting period (in hundredths)			30.00%
Percentage stock based compensation expense recognize over five years vesting period (in hundredths)			70.00%
Vesting period for recognition of 30 percent of stock based compensation expense (in years)			3Y
Vesting period for recognition of 70 percent of stock based compensation expense (in years)			5Y
Stock based compensation expense	$ 900,000	$ 700,000	$ 1,740,000	$ 1,263,000	$ 559,000	$ 1,754,000	$ 2,389,000	$ 3,328,000	$ 3,480,000	$ 2,588,000						$ 175,000	$ 494,000	$ 625,000	$ 870,000	$ 871,000	$ 577,000	$ 128,000	$ 462,000	$ 588,000	$ 848,000	$ 869,000	$ 686,000	$ 128,000	$ 399,000	$ 588,000	$ 805,000	$ 870,000	$ 655,000	$ 128,000	$ 399,000	$ 588,000	$ 805,000	$ 870,000	$ 670,000
Actual and projected stock based compensation expense for RSA shares and options [Abstract]
Actual stock based compensation expense	900,000	700,000	1,740,000	1,263,000	559,000	1,754,000	2,389,000	3,328,000	3,480,000	2,588,000						175,000	494,000	625,000	870,000	871,000	577,000	128,000	462,000	588,000	848,000	869,000	686,000	128,000	399,000	588,000	805,000	870,000	655,000	128,000	399,000	588,000	805,000	870,000	670,000
Compensation cost related to non-vested restricted stock awards and options not yet recognized	9,800,000		9,800,000								9,800,000
Stock options exercised (in shares)	2,000		2,000
Proceeds from Stock Options Exercised			58,000	0
Tax Benefit from Stock Options Exercised			$ 24,000	$ 0
Stock Repurchase Program [Abstract]
Incremental Class A shares authorized to buyback (in shares)													500,000
Shares repurchased (in shares)	3,369	268,621	228,102	430,209							7,572,154
Average price per share of repurchased shares (in dollars per share)	$ 44.08	$ 46.21	$ 44.34	$ 45.34							$ 40.74
Share available under program to repurchase (in shares)	345,265		345,265								345,265