Compensation Plans (Details) (USD $)	6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended			6 Months Ended		3 Months Ended		6 Months Ended	1 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Cash Bonus Plan [Member]	Jun. 30, 2013 Cash Bonus Plan [Member]	Jun. 30, 2014 Cash Bonus Plan [Member]	Jun. 30, 2013 Cash Bonus Plan [Member]	Jun. 30, 2014 Restricted Stock Units (RSUs) [Member]	Jun. 30, 2013 Restricted Stock Units (RSUs) [Member]	Jun. 30, 2014 Restricted Stock Units (RSUs) [Member]	Jun. 30, 2013 Restricted Stock Units (RSUs) [Member]	Jun. 30, 2014 Performance Shares [Member]	Jun. 30, 2013 Performance Shares [Member]	Jun. 30, 2014 Performance Shares [Member]	Jun. 30, 2013 Performance Shares [Member]	Jun. 30, 2014 Employee Stock Option [Member]	Jun. 30, 2014 Shares Issued to the Board of Directors [Member]	Jun. 30, 2013 Shares Issued to the Board of Directors [Member]	Jun. 30, 2014 Employee Stock [Member]	Jun. 30, 2013 Employee Stock [Member]	Jun. 30, 2014 Employee Stock [Member]	Jul. 23, 2014 Subsequent Event [Member] Restricted Stock Units (RSUs) [Member]	Jul. 23, 2014 Subsequent Event [Member] Performance Shares [Member]
Compensation plans
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription Rate																		15.00%		15.00%
Stock Issued During Period, Shares, Employee Stock Purchase Plans																		35,249	44,437
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription																		$ 25,000.00		$ 25,000.00
ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentOfOfferingDatePricePaid																				85.00%
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized																		1,200,000		1,200,000
Stock Issued During Period, Shares, Share-based Compensation, Gross																23,009	28,169
Multiplier Applied to PSU Awards at Settlement																						0.55
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period																					231,256	202,404
Cash Paid in Current Period for Bonus Compensation					41,700,000	16,000,000
Accrued Cash Bonus Plan Expense			6,200,000	5,300,000	12,800,000	10,900,000
RSUs, PSUs, and Director's Shares [Abstract]
Number of Common Shares to be Received Upon Settlement									1
Stock-based compensation expense	14,341,000	18,068,000					2,900,000	3,300,000	5,700,000	6,300,000	3,600,000	5,000,000	6,800,000	9,700,000		1,197,000	1,354,000
Unrecognized stock based compensation expense							12,800,000		12,800,000		11,300,000		11,300,000
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Low End of Range													0
Common stock awards vesting multiplier, high end of range													2
Share-based Compensation, Awards Other Than Options, Performance Measurement Period													3
Stock option activity
Stock options outstanding at the beginning of the period (in shares)															39,088
Stock options outstanding at the end of the period (in shares)															39,088
Weighted-Average Exercise Price
Stock options outstanding at the beginning of the period (in dollars per share)															$ 20.87
Stock options outstanding at the end of the period (in dollars per share)															$ 20.87
Aggregate Intrinsic Value
Vested at the end of the period															$ 2,472,000
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period																					243,389
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period, Net of Shares Withheld for Tax																					164,490	85,121
Shares Paid for Tax Withholding for Share Based Compensation																					78,899	45,042