Fair Value of Assets and Liabilities - Fair Value of Additional Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Jun. 17, 2020	Dec. 31, 2019
Senior Unsecured Notes, due 2021 at 4.25%
Fair Value of Assets and Liabilities
Interest rate stated percentage	4.25%
Senior Unsecured Notes, due 2022 at 5.00%
Fair Value of Assets and Liabilities
Interest rate stated percentage	5.00%
Senior Unsecured Notes, due 2023 at 4.50%
Fair Value of Assets and Liabilities
Interest rate stated percentage	4.50%
Senior Unsecured Notes, due 2024 at 4.65%
Fair Value of Assets and Liabilities
Interest rate stated percentage	4.65%
Senior Unsecured Notes, due 2024 at 4.35%
Fair Value of Assets and Liabilities
Interest rate stated percentage	4.35%
Senior Unsecured Notes, due 2025 at 4.50%
Fair Value of Assets and Liabilities
Interest rate stated percentage	4.50%
Senior Unsecured Notes, due 2025 at 7.50%
Fair Value of Assets and Liabilities
Interest rate stated percentage	7.50%	7.50%
Senior Unsecured Notes, due 2026 at 5.25%
Fair Value of Assets and Liabilities
Interest rate stated percentage	5.25%
Senior Unsecured Notes, due 2026 at 4.75%
Fair Value of Assets and Liabilities
Interest rate stated percentage	4.75%
Senior Unsecured Notes, due 2027 at 4.95%
Fair Value of Assets and Liabilities
Interest rate stated percentage	4.95%
Senior Unsecured Notes, due 2027 at 5.25%
Fair Value of Assets and Liabilities
Interest rate stated percentage	5.25%
Senior Unsecured Notes, due 2028 at 3.95%
Fair Value of Assets and Liabilities
Interest rate stated percentage	3.95%
Senior Unsecured Notes, due 2029 at 4.95%
Fair Value of Assets and Liabilities
Interest rate stated percentage	4.95%
Senior Unsecured Notes, due 2030 at 4.375%
Fair Value of Assets and Liabilities
Interest rate stated percentage	4.375%
Carrying amount
Fair Value of Assets and Liabilities
Total financial liabilities	$ 6,130,166		$ 5,287,658
Carrying amount | Senior Unsecured Notes, due 2021 at 4.25%
Fair Value of Assets and Liabilities
Total financial liabilities	0		398,379
Carrying amount | Senior Unsecured Notes, due 2022 at 5.00%
Fair Value of Assets and Liabilities
Total financial liabilities	498,032		496,821
Carrying amount | Senior Unsecured Notes, due 2023 at 4.50%
Fair Value of Assets and Liabilities
Total financial liabilities	499,596		499,432
Carrying amount | Senior Unsecured Notes, due 2024 at 4.65%
Fair Value of Assets and Liabilities
Total financial liabilities	348,700		348,295
Carrying amount | Senior Unsecured Notes, due 2024 at 4.35%
Fair Value of Assets and Liabilities
Total financial liabilities	819,546		818,075
Carrying amount | Senior Unsecured Notes, due 2025 at 4.50%
Fair Value of Assets and Liabilities
Total financial liabilities	347,118		346,431
Carrying amount | Senior Unsecured Notes, due 2025 at 7.50%
Fair Value of Assets and Liabilities
Total financial liabilities	789,006		0
Carrying amount | Senior Unsecured Notes, due 2026 at 5.25%
Fair Value of Assets and Liabilities
Total financial liabilities	344,212		343,083
Carrying amount | Senior Unsecured Notes, due 2026 at 4.75%
Fair Value of Assets and Liabilities
Total financial liabilities	446,515		445,905
Carrying amount | Senior Unsecured Notes, due 2027 at 4.95%
Fair Value of Assets and Liabilities
Total financial liabilities	395,405		394,649
Carrying amount | Senior Unsecured Notes, due 2027 at 5.25%
Fair Value of Assets and Liabilities
Total financial liabilities	442,370		0
Carrying amount | Senior Unsecured Notes, due 2028 at 3.95%
Fair Value of Assets and Liabilities
Total financial liabilities	391,908		390,759
Carrying amount | Senior Unsecured Notes, due 2029 at 4.95%
Fair Value of Assets and Liabilities
Total financial liabilities	418,102		417,307
Carrying amount | Senior Unsecured Notes, due 2030 at 4.375%
Fair Value of Assets and Liabilities
Total financial liabilities	389,656		388,522
Fair value
Fair Value of Assets and Liabilities
Total financial liabilities	6,361,902		5,499,211
Fair value | Senior Unsecured Notes, due 2021 at 4.25%
Fair Value of Assets and Liabilities
Total financial liabilities	0		406,838
Fair value | Senior Unsecured Notes, due 2022 at 5.00%
Fair Value of Assets and Liabilities
Total financial liabilities	510,285		526,500
Fair value | Senior Unsecured Notes, due 2023 at 4.50%
Fair Value of Assets and Liabilities
Total financial liabilities	505,280		520,478
Fair value | Senior Unsecured Notes, due 2024 at 4.65%
Fair Value of Assets and Liabilities
Total financial liabilities	347,893		364,277
Fair value | Senior Unsecured Notes, due 2024 at 4.35%
Fair Value of Assets and Liabilities
Total financial liabilities	819,328		848,847
Fair value | Senior Unsecured Notes, due 2025 at 4.50%
Fair Value of Assets and Liabilities
Total financial liabilities	346,462		361,783
Fair value | Senior Unsecured Notes, due 2025 at 7.50%
Fair Value of Assets and Liabilities
Total financial liabilities	926,404		0
Fair value | Senior Unsecured Notes, due 2026 at 5.25%
Fair Value of Assets and Liabilities
Total financial liabilities	354,996		369,185
Fair value | Senior Unsecured Notes, due 2026 at 4.75%
Fair Value of Assets and Liabilities
Total financial liabilities	448,506		464,315
Fair value | Senior Unsecured Notes, due 2027 at 4.95%
Fair Value of Assets and Liabilities
Total financial liabilities	404,328		414,012
Fair value | Senior Unsecured Notes, due 2027 at 5.25%
Fair Value of Assets and Liabilities
Total financial liabilities	491,918		0
Fair value | Senior Unsecured Notes, due 2028 at 3.95%
Fair Value of Assets and Liabilities
Total financial liabilities	388,146		393,940
Fair value | Senior Unsecured Notes, due 2029 at 4.95%
Fair Value of Assets and Liabilities
Total financial liabilities	430,064		434,248
Fair value | Senior Unsecured Notes, due 2030 at 4.375%
Fair Value of Assets and Liabilities
Total financial liabilities	$ 388,292		$ 394,788