Organization and Summary of Significant Accounting Policies - Fair value (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Fair Value of Financial Instruments
Debt instrument, Carrying Value	$ 2,163.2	$ 1,877.1
5.75% senior subordinated notes due 2022
Fair Value of Financial Instruments
Interest rate (as a percent)	5.75%	5.75%
Debt instrument, Carrying Value	$ 545.9	$ 545.1
5.75% senior subordinated notes due 2022 \| Fair Value, Inputs, Level 2
Fair Value of Financial Instruments
Debt instrument, Carrying Value	545.9	545.1
Debt instrument, Fair Value	$ 562.3	$ 567.6
5.375% senior subordinated Notes Due 2024
Fair Value of Financial Instruments
Interest rate (as a percent)	5.375%	5.375%
Debt instrument, Carrying Value	$ 297.2	$ 296.8
5.375% senior subordinated Notes Due 2024 \| Fair Value, Inputs, Level 2
Fair Value of Financial Instruments
Debt instrument, Carrying Value	297.2	296.8
Debt instrument, Fair Value	$ 300.2	$ 293.0
5.50% senior subordinated notes due 2026
Fair Value of Financial Instruments
Interest rate (as a percent)	5.50%	5.50%
Debt instrument, Carrying Value	$ 494.4	$ 493.7
5.50% senior subordinated notes due 2026 \| Fair Value, Inputs, Level 2
Fair Value of Financial Instruments
Debt instrument, Carrying Value	494.4	493.7
Debt instrument, Fair Value	$ 505.0	489.4
3.75% senior subordinated notes due 2020
Fair Value of Financial Instruments
Interest rate (as a percent)	3.75%
Debt instrument, Carrying Value	$ 296.5
3.75% senior subordinated notes due 2020 \| Fair Value, Inputs, Level 2
Fair Value of Financial Instruments
Debt instrument, Carrying Value	296.5
Debt instrument, Fair Value	301.7
Mortgage facilities
Fair Value of Financial Instruments
Debt instrument, Carrying Value	235.5	199.9
Mortgage facilities \| Fair Value, Inputs, Level 2
Fair Value of Financial Instruments
Debt instrument, Carrying Value	235.5	199.9
Debt instrument, Fair Value	$ 233.4	$ 195.6

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13433-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13476-108611

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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