Summary of Significant Accounting Policies Recently Issued Accounting Standards (Details) - USD ($)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Operating Activities	$ 336,631,000	$ 341,062,000	$ 379,121,000
Net Cash Provided by (Used in) Investing Activities	(465,652,000)	614,927,000	(89,660,000)
Net Cash Provided by (Used in) Financing Activities	96,231,000	(939,507,000)	(331,860,000)
Accounting Standards Update 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Financing Activities	96,231,000	(939,507,000)	(331,860,000)
Accounting Standards Update 2016-09 [Member] \| Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Financing Activities	101,338,000	(934,135,000)	(327,627,000)
Accounting Standards Update 2016-09 [Member] \| Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Operating Activities	5,107,000	5,372,000	4,233,000
Net Cash Provided by (Used in) Financing Activities	(5,107,000)	(5,372,000)	(4,233,000)
Accounting Standards Update 2016-18 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Operating Activities	336,631,000	341,062,000	379,121,000
Net Cash Provided by (Used in) Investing Activities	(465,652,000)	614,927,000	(89,660,000)
Accounting Standards Update 2016-18 [Member] \| Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Operating Activities	331,337,000	333,021,000	385,366,000
Net Cash Provided by (Used in) Investing Activities	(465,652,000)	613,402,000	(89,660,000)
Accounting Standards Update 2016-18 [Member] \| Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Operating Activities	187,000	2,669,000	(10,478,000)
Net Cash Provided by (Used in) Investing Activities	$ 0	$ 1,525,000	$ 0

Amount of cash inflow (outflow) from financing activities, including discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit.

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Amount of cash inflow (outflow) from investing activities, including discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets.

+ References

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Amount of cash inflow (outflow) from operating activities, including discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 24
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3521-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3536-108585

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