Shareholders' Equity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended	1 Months Ended		12 Months Ended			1 Months Ended				12 Months Ended
	Dec. 31, 2012 Y	Jun. 30, 2012 RSU director	Oct. 31, 2010 RSU	Dec. 31, 2012 RSU	Dec. 31, 2011 RSU	Dec. 31, 2010 RSU	May 31, 2011 RSA	May 31, 2010 RSA	May 31, 2009 RSA	May 31, 2008 RSA	Dec. 31, 2012 RSA	Dec. 31, 2012 SAR Y	Dec. 31, 2011 SAR	Dec. 31, 2010 SAR	Dec. 31, 2012 Common Stock RSU
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of issuable common shares	2,654,000
Summary of Activity of RSU, RSA and SAR [Rollforward]
Outstanding and unvested at beginning of period				594,000							5,046	1,812,079
Granted		13,716	454,000	13,716
Vested				(140,000)							(5,046)
Outstanding and unvested at end of period				467,716	594,000						0	1,812,079	1,812,079
Unrecognized compensation cost (in dollars)				$ 6,511							$ 0
Unrecognized compensation cost, period for recognition (in years)	2
RSUs issued to each non-employee director		2,286
Number of non-employee directors receiving grants		6
Total fair value of RSU grants		300	13,900
Award vesting period		1 year
Exercise of restricted stock units, shares															94,176
RSA issued to each non-employee director							700	700	700	700
Stock-based compensation expense				$ 3,900	$ 4,500	$ 4,700						$ 0	$ 0	$ 728
Fair Value Assumptions and Methodology
Expected volatility, minimum												29.00%
Expected volatility, maximum												31.00%
Expected term (in years)												7
Risk-free rate, minimum												4.30%
Risk-free rate, maximum												4.70%
Expected dividend yield												0.00%
Expected forfeiture rate												0.00%
Weighted Average Exercise Price, Outstanding												$ 36.16	$ 36.16
SAR outstanding, weighted average contractual term remaining												3 years 6 months	4 years 6 months