Senior Notes (Summary of Senior Notes) (Details) - USD ($) $ in Thousands		Dec. 31, 2023	Dec. 31, 2022	May 31, 2020	Oct. 31, 2017	Jul. 31, 2014
Debt Instrument [Line Items]
Long-term Debt, gross		$ 1,125,000	$ 1,125,000
Debt issuance costs, net		(9,371)	(10,446)
Senior notes, net		1,115,629	1,114,554
Senior notes 4.25% due 2024 [Member]
Debt Instrument [Line Items]
Long-term Debt, gross	[1]	500,000	500,000
Senior notes, net						$ 300,000
Senior notes 4.00% due 2030 [Member]
Debt Instrument [Line Items]
Long-term Debt, gross	[2]	400,000	400,000
Senior notes, net				$ 400,000
Senior notes 5.20% due 2047 [Member]
Debt Instrument [Line Items]
Long-term Debt, gross	[3]	$ 225,000	$ 225,000
Senior notes, net					$ 200,000

[1] In July 2014, we sold in a registered underwritten public offering, $300.0 million in aggregate principal amount of 4.25% senior notes due July 2024. Interest on these senior notes is payable semi-annually in arrears. We may redeem the notes in whole or in part, at our option, at a redemption price equal to 100% of their principal amount, plus a “make-whole” premium and accrued and unpaid interest, if any, to the date of redemption. In July 2016, we issued an additional $200.0 million in aggregate principal amount of 4.25% senior notes due 2024.

[2] In May 2020, we sold in a registered underwritten public offering, $400.0 million in aggregate principal amount of 4.00% senior notes due May 2030. Interest on these senior notes is payable semi-annually in arrears. We may redeem the notes in whole or in part, at our option, at a redemption price equal to the greater of a) 100% of their principal amount, or b) discounted present value at Treasury rate plus 50 basis points prior to February 15, 2030, and on or after February 15, 2030, at 100% of their principal amount, and accrued and unpaid interest, if any, to the date of redemption.

[3] In October 2017, we completed the pricing of a registered underwritten public offering of $200.0 million in aggregate principal amount of 5.20% senior notes due October 2047. Interest on the senior notes is payable quarterly in arrears. We may redeem some or all of the senior notes at any time at a redemption price equal to 100% of the principal amount of the notes being redeemed plus accrued interest thereon to the redemption date. On October 27, 2017, we completed the sale of an additional $25.0 million aggregate principal amount of Notes pursuant to the over-allotment option.