Shared Based Awards (Details) (USD $)	12 Months Ended																	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2015 Stock Option [Member]	Dec. 31, 2014 Stock Option [Member]	Dec. 31, 2013 Stock Option [Member]	Dec. 31, 2012 Stock Option [Member]	Dec. 31, 2011 Stock Option [Member]	Dec. 31, 2011 Employee Stock [Member]	Dec. 31, 2011 Stock Options [Member]	Dec. 31, 2010 Stock Options [Member]	Dec. 31, 2009 Stock Options [Member]	Dec. 31, 2011 Share awards - initial authorized for issuance [Member]	Dec. 31, 2011 Share awards available for issuance adjustment [Member]	Dec. 31, 2011 Share awards - total available for issuance [Member]	Dec. 31, 2011 Employee Stock [Member]	Dec. 31, 2010 Employee Stock [Member]	Dec. 31, 2009 Employee Stock [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock compensation			$ 4,016,000	$ 3,471,000	$ 2,708,000
Tax benefit from recognized stock compensation expense			1,400,000	1,200,000	900,000
Indirect tax benefit from stock options			800,000	400,000
Authorized share in stock incentive plan															650,000	251,700	901,700
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected term (in years)												3.0	3.4	5.8				0.5	0.5	0.5
Expected stock price volatility												35.30%	40.20%	37.40%				26.00%	26.50%	48.30%
Risk-free interest rate												0.90%	0.80%	2.40%				0.40%	0.20%	0.40%
Expected dividend yield												0.00%	0.00%	0.00%				0.00%	0.00%	0.00%
Weighted average grant price												$ 43.27	$ 34.70	$ 35.24
Weighted average grant date fair value												$ 10.72	$ 10.18	$ 12.98
Stock options granted, shares			290,000	243,000	254,000
Stock options granted, value			3,100,000	2,500,000	3,300,000
Unamortized stock compensation cost						200,000	900,000	2,000,000	3,200,000	6,300,000	100,000
Option vesting period low end of range		2012
Vesting period high end of range	2015
Number of unvested option grants			160
Number of unvested options			798,300
Stock option activity [Abstract]
Outstanding options, shares			2,745,428	2,919,194
Outstanding options, weighted average exercise price			$ 33.28	$ 29.77
Granted options, shares			290,000
Granted options, weighted average exercise price			$ 43.27
Exercised options, shares			(459,266)
Exercised options, weighted average exercise price			$ 17.36
Forfeited options, shares			(4,500)
Forfeited options, weighted average exercise price			$ 27.48
Exercisable options, shares			1,765,397
Exercisable options, weighted average exercise price			$ 31.97
Available for grant, 2011 Plan, shares			786,700
Intrinsic value [Abstract]
Intrinsic value of stock options exercised												11,500,000	4,400,000	300,000				500,000	300,000	400,000
Intrinsic value of stock options outstanding			32,200,000
Intrinsic value of stock options exercisable			$ 23,000,000
Weighted average term [Abstract]
Weighted average remaining contractual term, options outstanding			4.5
Weighted average remaining contractual term, options exercisable			2.9
ESPP [Abstract]
Employee stock purchase plan, shares issued			57,643	53,739	46,401
Shares available employee stock purchase plan			381,853