Significant Accounting Policies - Recently Adopted Accounting Standards (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other current assets	$ (37,211)		$ (33,938)
Deferred income taxes	(146,574)		(128,007)
Retained earnings	(2,615,131)		(2,342,079)
Operating lease, right-of-use asset	82,374
Present value of lease liabilities	$ 85,163
Accounting Standards Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption					$ 0
Accounting Standards Update 2016-16
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption					(645)
Other current assets				$ 7,300
Deferred income taxes				6,700
Retained earnings				600
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption			28
Operating lease, right-of-use asset		$ 68,000
Present value of lease liabilities		68,000
Finance lease, liability		68,000
Finance lease, right-of-use asset		$ 68,000
Retained Earnings | Accounting Standards Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption					6,435
Retained Earnings | Accounting Standards Update 2018-02 | New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption				(6,400)
Retained Earnings | Accounting Standards Update 2016-16
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption					$ (645)
Retained Earnings | Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption			$ 28
AOCI Attributable to Parent | Accounting Standards Update 2018-02 | New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption				$ 6,400