Summary of Significant Accounting Policies - New Accounting Pronouncements (Details) - USD ($) $ in Thousands		12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
New Accounting Pronouncement Effect on Equity
New Accounting Pronouncement Effect Of Adoption On Additional Paid In Capital	$ 2,458,889
New Accounting Pronouncement Effect Of Adoption On Retained Earnings	652,704
New Accounting Pronouncement Effect Of Adoption On Cash Flow Amortization Of Deferred Stock Compensation		$ 9,695	$ 9,063
New Accounting Pronouncement Effect Of Adoption On Cash Flow Accrued Payroll And Employee Benefits		(2,060)	2,776
New Accounting Pronouncement Effect Of Adoption On Cash Flow Net Cash Provided By Operating Activities		309,325	282,369
New Accounting Pronouncement Effect Of Adoption On Cash Flow Repurchase Of Common Stock For Employee Withholding Obligations		(9,264)	(3,774)
New Accounting Pronouncement Effect Of Adoption On Cash Flow Net Cash Used In Financing Activities		(431,707)	242,098
Previously Reported Member
New Accounting Pronouncement Effect on Equity
New Accounting Pronouncement Effect Of Adoption On Additional Paid In Capital	2,458,735
New Accounting Pronouncement Effect Of Adoption On Retained Earnings	652,858
New Accounting Pronouncement Effect Of Adoption On Cash Flow Amortization Of Deferred Stock Compensation		6,536	6,221
New Accounting Pronouncement Effect Of Adoption On Cash Flow Accrued Payroll And Employee Benefits		(8,165)	1,844
New Accounting Pronouncement Effect Of Adoption On Cash Flow Net Cash Provided By Operating Activities		300,061	278,595
New Accounting Pronouncement Effect Of Adoption On Cash Flow Net Cash Used In Financing Activities		(422,443)	245,872
Accounting Standards Update 2016-09 Member
New Accounting Pronouncement Effect on Equity
New Accounting Pronouncement Effect Of Adoption On Additional Paid In Capital	154
New Accounting Pronouncement Effect Of Adoption On Retained Earnings	$ (154)
New Accounting Pronouncement Effect Of Adoption On Cash Flow Amortization Of Deferred Stock Compensation		3,159	2,842
New Accounting Pronouncement Effect Of Adoption On Cash Flow Accrued Payroll And Employee Benefits		6,105	932
New Accounting Pronouncement Effect Of Adoption On Cash Flow Net Cash Provided By Operating Activities		9,264	3,774
New Accounting Pronouncement Effect Of Adoption On Cash Flow Repurchase Of Common Stock For Employee Withholding Obligations		(9,264)	(3,774)
New Accounting Pronouncement Effect Of Adoption On Cash Flow Net Cash Used In Financing Activities		$ (9,264)	$ (3,774)