Fair Value of Assets and Liabilities - Liabilities (Details) - USD ($) $ in Thousands	1 Months Ended
	Feb. 25, 2021	Dec. 31, 2020	Dec. 31, 2019
Joint venture | Life Science Property
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Equity method investment ownership percentage		55.00%
Senior Unsecured Notes Due 2031 | Subsequent Event
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Principal amount of debt	$ 500
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Secured and secured debt		$ 3,299,762	$ 2,518,410
Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Secured and secured debt		$ 3,489,902	2,587,528
Senior unsecured notes, 6.750% coupon rate, due in 2020 | Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Coupon		6.75%
Secured and secured debt		$ 0	199,862
Senior unsecured notes, 6.750% coupon rate, due in 2020 | Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Secured and secured debt		$ 0	200,306
Senior unsecured notes, 6.750% coupon rate, due in 2021 | Senior Unsecured Notes Due June 2021 | Subsequent Event
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Coupon	6.75%
Debt extinguishment, amount	$ 200,000
Senior unsecured notes, 6.750% coupon rate, due in 2021 | Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Coupon		6.75%
Secured and secured debt		$ 299,273	298,486
Senior unsecured notes, 6.750% coupon rate, due in 2021 | Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Secured and secured debt		$ 303,891	318,042
Senior unsecured notes, 4.750% coupon rate, due in 2024 | Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Coupon		4.75%
Secured and secured debt		$ 249,068	248,788
Senior unsecured notes, 4.750% coupon rate, due in 2024 | Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Secured and secured debt		$ 256,258	260,683
Senior unsecured notes, 9.750% coupon rate, due in 2025 | Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Coupon		9.75%
Secured and secured debt		$ 984,359	0
Senior unsecured notes, 9.750% coupon rate, due in 2025 | Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Secured and secured debt		$ 1,135,800	0
Senior unsecured notes, 4.750% coupon rate, due in 2028 | Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Coupon		4.75%
Secured and secured debt		$ 490,925	489,652
Senior unsecured notes, 4.750% coupon rate, due in 2028 | Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Secured and secured debt		$ 502,648	506,155
Senior unsecured notes, 5.625% coupon rate, due in 2042 | Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Coupon		5.625%
Secured and secured debt		$ 341,802	341,421
Senior unsecured notes, 5.625% coupon rate, due in 2042 | Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Secured and secured debt		$ 330,120	346,500
Senior unsecured notes, 6.250% coupon rate, due in 2046 | Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Coupon		6.25%
Secured and secured debt		$ 242,762	242,472
Senior unsecured notes, 6.250% coupon rate, due in 2046 | Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Secured and secured debt		245,000	258,700
Senior unsecured notes 4.37 percent due 2031 | Senior Unsecured Notes Due 2031 | Subsequent Event
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Coupon	4.375%
Secured debts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Principal mortgage obligations		3,015
Deb issuance costs		25
Secured debts | Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Secured and secured debt		691,573	697,729
Secured debts | Estimated Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Secured and secured debt		$ 716,185	$ 697,142