Debt (Tables)

6 Months Ended

Jun. 30, 2021

Debt Disclosure [Abstract]

Schedule of Long-term Debt

The following table presents the carrying amounts and estimated fair values of our convertible senior notes that are not recorded at fair value on our consolidated balance sheets:

	June 30, 2021				December 31, 2020
Issuance	Net Carrying Amount		Estimated Fair Value		Net Carrying Amount		Estimated Fair Value
2023 notes	$	23,428	$	50,106	$	22,482	$	59,894
2025 notes	649,403		747,808		488,268		802,083
2027 notes	562,114		571,107		—		—

The following table summarizes borrowings under these facilities as of the periods presented:

	June 30, 2021						December 31, 2020
Lender	Borrowing Capacity		Outstanding Borrowings		Weighted-Average Interest Rate on Outstanding Borrowings		Borrowing Capacity		Outstanding Borrowings		Weighted-Average Interest Rate on Outstanding Borrowings
Western Alliance Bank	$	50,000	$	17,825	3.25	%	$	50,000	$	18,277	3.25	%
Texas Capital Bank, N.A.	40,000		17,398		3.35	%	40,000		12,903		3.35	%
Flagstar Bank, FSB	15,000		11,202		3.00	%	15,000		7,849		3.00	%
Total	$	105,000	$	46,425	—		$	105,000	$	39,029	—

The following table summarizes borrowings under this facility as of the periods presented:

	June 30, 2021						December 31, 2020
Lender	Borrowing Capacity		Outstanding Borrowings		Weighted-Average Interest Rate on Outstanding Borrowings		Borrowing Capacity		Outstanding Borrowings		Weighted-Average Interest Rate on Outstanding Borrowings
Goldman Sachs Bank USA	$	125,000	$	123,770	3.30	%	$	100,000	$	23,949	4.40	%

Convertible Debt

We have issued convertible senior notes with the following characteristics:

Issuance	Maturity Date	Stated Cash Interest Rate		Effective Interest Rate		First Interest Payment Date	Semi-Annual Interest Payment Dates	Conversion Rate
2023 notes	July 15, 2023	1.75	%	2.45	%	January 15, 2019	January 15; July 15	32.7332
2025 notes	October 15, 2025	—	%	0.42	%	—	—	13.7920
2027 notes	April 1, 2027	0.50	%	0.90	%	October 1, 2021	April 1; October 1	10.6920

We issued our 2023 notes on July 23, 2018, with an aggregate principal amount of $143,750. Subsequent to the issuance date, we repurchased or settled conversions of an aggregate of $120,012 of our 2023 notes.

We issued our 2025 notes on October 20, 2020, with an aggregate principal amount of $661,250.

We issued our 2027 notes on March 25, 2021, with an aggregate principal amount of $500,000. Our proceeds from the issuance, after deducting the initial purchasers' discount and offering expenses payable by us, were $488,234. On April 5, 2021 and pursuant to the initial purchasers exercise of their option to purchase additional 2027 notes, we issued additional 2027 notes with an aggregate principal amount of $75,000. Our proceeds from the issuance, after deducting the initial purchaser's discount and offering expenses payable by us, were $73,296.

The components of our convertible senior notes were as follows:

	June 30, 2021
Issuance	Aggregate Principal Amount		Unamortized Debt Discount		Unamortized Debt Issuance Costs		Net Carrying Amount
2023 notes	$	23,738	$	—	$	310	$	23,428
2025 notes	661,250		—		11,847		649,403
2027 notes	575,000		—		12,886		562,114

	December 31, 2020
Issuance	Aggregate Principal Amount		Unamortized Debt Discount		Unamortized Debt Issuance Costs		Net Carrying Amount
2023 notes	$	25,626	$	2,776	$	368	$	22,482
2025 notes	661,250		163,077		9,905		488,268

Interest Income and Interest Expense Disclosure

	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
2023 notes
Contractual interest expense	$	104	$	629	$	208	$	1,258
Amortization of debt discount	—		1,405		—		2,796
Amortization of debt issuance costs	39		187		110		373
Total interest expense	$	143	$	2,221	$	318	$	4,427
2025 notes
Contractual interest expense	—		—		—		—
Amortization of debt discount	—		—		—		—
Amortization of debt issuance costs	690		—		1,380		—
Total interest expense	$	690	$	—	$	1,380	$	—
2027 notes
Contractual interest expense	715		—		749		—
Amortization of debt discount	—		—		—		—
Amortization of debt issuance costs	557		—		585		—
Total interest expense	$	1,272	$	—	$	1,334	$	—
Total
Contractual interest expense	819		629		957		1,258
Amortization of debt discount	—		1,405		—		2,796
Amortization of debt issuance costs	1,286		187		2,075		373
Total interest expense	$	2,105	$	2,221	$	3,032	$	4,427