Debt - (Tables)

12 Months Ended

Dec. 31, 2021

Debt Disclosure [Abstract]

Schedule of Long-term Debt Instruments

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:

	December 31, 2021				December 31, 2020
Issuance	Net Carrying Amount		Estimated Fair Value		Net Carrying Amount		Estimated Fair Value
2023 notes	$	23,280	$	34,487	$	22,482	$	59,894
2025 notes	650,783		593,366		488,268		802,083
2027 notes	563,234		467,814		—		—

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

	December 31, 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	$	17,089	3.00	%	$	50,000	$	18,277	3.25	%
Texas Capital Bank, N.A.	40,000		11,852		3.01	%	40,000		12,903		3.35	%
Flagstar Bank, FSB	25,000		4,102		3.00	%	15,000		7,849		3.00	%
Total	$	115,000	$	33,043	—		$	105,000	$	39,029	—

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

	December 31, 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	$	200,000	$	199,781	3.30	%	$	100,000	$	23,949	4.40	%

Convertible Senior Notes

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 $120,238 of our 2023 notes. On July 20, 2021, our 2023 notes became redeemable by us, but we did not exercise our redemption right during the three months ended December 31, 2021.

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 and April 5, 2021, with an aggregate principal amount of $575,000.

The components of the convertible senior notes are as follows:

	December 31, 2021
Issuance	Aggregate Principal Amount		Unamortized Debt Discount		Unamortized Debt Issuance Costs		Net Carrying Amount
2023 notes	$	23,512	$	—	$	232	$	23,280
2025 notes	661,250		—		10,467		650,783
2027 notes	575,000		—		11,766		563,234

	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

	Year End December 31,
	2021		2020		2019
2023 notes
Contractual interest expense	$	413	$	2,113	$	2,516
Amortization of debt discount	—		4,735		5,405
Amortization of debt issuance costs	189		623		724
Total interest expense	$	602	$	7,471	$	8,645
2025 notes
Contractual interest expense	—		—		—
Amortization of debt discount	—		5,693		—
Amortization of debt issuance costs	2,760		346		—
Total interest expense	$	2,760	$	6,039	$	—
2027 notes
Contractual interest expense	2,187		—		—
Amortization of debt discount	—		—		—
Amortization of debt issuance costs	1,705		—		—
Total interest expense	$	3,892	$	—	$	—
Total
Contractual interest expense	2,600		2,113		2,516
Amortization of debt discount	—		10,428		5,405
Amortization of debt issuance costs	4,654		969		724
Total interest expense	$	7,254	$	13,510	$	8,645