Debt Instrument, Convertible, Principal Amount Per Conversion Ratio

No definition available.

Name:	star_DebtInstrumentConvertiblePrincipalAmountPerConversionRatio
Namespace Prefix:	star_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28541-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.8)
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

+ Details

Name:	us-gaap_AmortizationOfDebtDiscountPremium
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Including the current and noncurrent portions, carrying amount of debt identified as being convertible into another form of financial instrument (typically the entity's common stock) as of the balance sheet date, which originally required full repayment more than twelve months after issuance or greater than the normal operating cycle of the company.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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=120400017&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-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=120391452&loc=d3e13212-122682

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-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=120398452&loc=d3e534808-122878

+ Details

Name:	us-gaap_ConvertibleDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-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=120391452&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-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=120398452&loc=d3e534808-122878

+ Details

Name:	us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying amount of the equity component of convertible debt which may be settled in cash upon conversion.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6031897-161870

+ Details

Name:	us-gaap_DebtInstrumentConvertibleCarryingAmountOfTheEquityComponent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The price per share of the conversion feature embedded in the debt instrument.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6031898-161870

+ Details

Name:	us-gaap_DebtInstrumentConvertibleConversionPrice1
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21521-112644

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21506-112644

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(5))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

Name:	us-gaap_DebtInstrumentConvertibleConversionRatio1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6036836-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-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=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after accumulated amortization, of debt discount.

+ References

+ Details

Name:	us-gaap_DebtInstrumentUnamortizedDiscount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of unamortized debt discount (premium) and debt issuance costs.

+ References

+ Details

Name:	us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of interest capitalized during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391

+ Details

Name:	us-gaap_InterestCostsCapitalized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of the cost of borrowed funds accounted for as interest expense for debt.

+ References

+ Details

Name:	us-gaap_InterestExpenseDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-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=120400017&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-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=120398452&loc=d3e534808-122878

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-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=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentAxis=star_A2016SeniorSecuredCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=star_Unsecured3.125SeniorConvertibleNotesDueSeptember2022Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=star_SecuredRevolvingCreditFacilityDueSeptember2022Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_FederalFundsEffectiveSwapRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	star_DebtInstrumentInterestRateCategoryAxis=star_InterestRateCategoryTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_BaseRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	star_DebtInstrumentInterestRateCategoryAxis=star_InterestRateCategoryOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=star_SecuredTermLoansCollateralizedByLoansNetLeaseAssetsDueThrough2026Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=star_UnsecuredDebtNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=star_UnsecuredSixPercentSeniorNotesDueApril2022Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=star_Unsecured5.25SeniorNotesDueSeptember2022Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=star_Unsecured4.75SeniorNotesDueOctober2024Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=star_Unsecured4.25SeniorNotesDueAugust2025Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=star_UnsecuredDebtOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=star_OtherDebtSecuritiesDueOctober2035Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Debt Obligations, net - Schedule of Debt (Details)	1 Months Ended		3 Months Ended		6 Months Ended
Debt Obligations, net - Schedule of Debt (Details)	Sep. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2020 USD ($) $ / shares	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) $ / shares	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Nov. 30, 2019 USD ($)	Oct. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)
Debt Instrument [Line Items]
Total debt obligations			$ 3,325,246,000		$ 3,325,246,000		$ 3,436,038,000
Debt discounts and deferred financing costs, net			(42,184,000)		(42,184,000)		(48,958,000)
Debt obligations, net			3,283,062,000		3,283,062,000		3,387,080,000
Interest costs capitalized			$ 600,000	$ 3,500,000	$ 1,100,000	$ 6,500,000
Senior Term Loan \| LIBOR
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)					1.00%
3.125% Senior Convertible Notes
Debt Instrument [Line Items]
Stated interest rates (as a percent)			3.125%	3.125%	3.125%	3.125%
Secured Credit Facility
Debt Instrument [Line Items]
Total debt obligations			$ 1,212,746,000		$ 1,212,746,000		1,212,993,000
Debt discounts and deferred financing costs, net			(6,880,000)		(6,880,000)
Debt obligations, net			1,205,866,000		1,205,866,000
Secured Credit Facility \| Revolving Credit Facility
Debt Instrument [Line Items]
Total debt obligations			0		$ 0		0
Debt instrument term (in years)					1 year
Secured Credit Facility \| Revolving Credit Facility \| Federal Funds Rate
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)					0.50%
Secured Credit Facility \| Revolving Credit Facility \| LIBOR
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)					2.00%
Secured Credit Facility \| Revolving Credit Facility \| LIBOR \| Minimum
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)	2.00%				1.00%
Secured Credit Facility \| Revolving Credit Facility \| LIBOR \| Minimum \| Interest Rate Category Two
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)					2.00%
Secured Credit Facility \| Revolving Credit Facility \| LIBOR \| Maximum
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)	2.50%
Secured Credit Facility \| Revolving Credit Facility \| LIBOR \| Maximum \| Interest Rate Category Two
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)					2.50%
Secured Credit Facility \| Revolving Credit Facility \| Base Rate \| Minimum
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)	1.00%
Secured Credit Facility \| Revolving Credit Facility \| Base Rate \| Minimum \| Interest Rate Category One
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)					1.00%
Secured Credit Facility \| Revolving Credit Facility \| Base Rate \| Maximum
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)	1.50%
Secured Credit Facility \| Revolving Credit Facility \| Base Rate \| Maximum \| Interest Rate Category One
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)					1.50%
Secured Credit Facility \| Senior Term Loan
Debt Instrument [Line Items]
Total debt obligations			491,875,000		$ 491,875,000		491,875,000
Debt instrument, face amount		$ 650,000,000.0
Secured Credit Facility \| Senior Term Loan \| Federal Funds Rate
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)					0.50%
Secured Credit Facility \| Senior Term Loan \| LIBOR
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)		2.75%			2.75%
Secured Credit Facility \| Senior Term Loan \| LIBOR \| Maximum
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)					1.75%
Secured Credit Facility \| Mortgages collateralized by net lease assets
Debt Instrument [Line Items]
Total debt obligations			$ 720,871,000		$ 720,871,000		721,118,000
Weighted average interest rate (percent)			4.40%		4.40%
Secured Credit Facility \| Mortgages collateralized by net lease assets \| Minimum
Debt Instrument [Line Items]
Stated interest rates (as a percent)			1.71%		1.71%
Secured Credit Facility \| Mortgages collateralized by net lease assets \| Maximum
Debt Instrument [Line Items]
Stated interest rates (as a percent)			7.26%		7.26%
Unsecured notes
Debt Instrument [Line Items]
Total debt obligations			$ 2,012,500,000		$ 2,012,500,000		2,123,045,000
Unsecured notes \| 6.00% Senior Notes
Debt Instrument [Line Items]
Total debt obligations			$ 0		$ 0		$ 110,545,000
Stated interest rates (as a percent)			6.00%		6.00%		6.00%
Unsecured notes \| 5.25% Senior Notes
Debt Instrument [Line Items]
Total debt obligations			$ 400,000,000		$ 400,000,000		$ 400,000,000
Stated interest rates (as a percent)			5.25%		5.25%
Unsecured notes \| 3.125% Senior Convertible Notes
Debt Instrument [Line Items]
Total debt obligations			$ 287,500,000		$ 287,500,000		287,500,000
Debt obligations, net			$ 271,800,000		$ 271,800,000		$ 268,700,000
Stated interest rates (as a percent)			3.125%		3.125%		3.125%		3.125%
Convertible debt, conversion ratio (in shares per par value)					0.0691041
Convertible debt, conversion ratio principal amount					$ 1,000
Convertible debt, conversion price (in dollars per share) \| $ / shares			$ 14.47		$ 14.47
Liability component of convertible debt									$ 34,000,000.0	$ 221,800,000
Equity component of convertible debt									3,400,000	$ 22,500,000
Debt instrument, face amount									$ 37,500,000
Unamortized discount			$ 12,900,000		$ 12,900,000		$ 15,500,000
Contractual interest			2,200,000	$ 2,200,000	4,500,000	$ 4,500,000
Amortization of debt discount			$ 1,300,000	$ 1,200,000	$ 2,600,000	$ 2,500,000
Effective interest rate (percent)			5.20%		5.20%
Unsecured notes \| 4.75% Senior Notes
Debt Instrument [Line Items]
Total debt obligations			$ 775,000,000		$ 775,000,000		775,000,000
Stated interest rates (as a percent)	4.75%		4.75%		4.75%			4.75%
Debt instrument, face amount	$ 675,000,000.0							$ 100,000,000.0
Effective interest rate (percent)								4.29%
Unsecured notes \| 4.25% Senior Notes
Debt Instrument [Line Items]
Total debt obligations			$ 550,000,000		$ 550,000,000		$ 550,000,000
Stated interest rates (as a percent)			4.25%		4.25%		4.25%
Debt instrument, face amount							$ 550,000,000.0
Other debt obligations \| Trust preferred securities
Debt Instrument [Line Items]
Total debt obligations			$ 100,000,000		$ 100,000,000		$ 100,000,000
Other debt obligations \| Trust preferred securities \| LIBOR
Debt Instrument [Line Items]
Basis point spread on variable interest rate (as a percent)					1.50%