Derivative and Hedging Activities (Interest Rate Derivatives) (Details) ₩ in Thousands, $ in Thousands	6 Months Ended
	Dec. 31, 2020	Jun. 30, 2020 USD ($)	Jun. 30, 2020 KRW (₩)
Cash flow hedges of interest rate risk [Abstract]
Noncontrolling Interest, Ownership Percentage by Parent		70.00%	70.00%
Line of Credit [Member]
Cash flow hedges of interest rate risk [Abstract]
Debt Instrument, Description of Variable Rate Basis	LIBOR
Line of Credit Facility, Maximum Borrowing Capacity		$ 1,100,000
Unsecured Debt 275M Term Loan [Member]
Cash flow hedges of interest rate risk [Abstract]
Debt Instrument, Description of Variable Rate Basis	LIBOR
Unsecured Debt		$ 275,000
Consolidated Subsidiaries Interest Rate Swap 1 [Domain]
Cash flow hedges of interest rate risk [Abstract]
Noncontrolling Interest, Ownership Percentage by Parent		100.00%	100.00%
Derivative, Notional Amount		$ 100,000
Derivative, Fixed Interest Rate		2.14%	2.14%
Derivative, Basis Spread on Variable Rate		1.55%	1.55%
Total Swapped Rate On Loan		3.69%	3.69%
Derivative, Maturity Date		Feb. 01, 2022
Consolidated Subsidiaries Interest Rate Swap 1 [Domain] | Unsecured Debt 275M Term Loan [Member]
Cash flow hedges of interest rate risk [Abstract]
Unsecured Debt		$ 275,000
Derivative, Lower Range of Basis Spread, Variable Rate		1.15%	1.15%
Derivative, Higher Range of Basis Spread, Variable Rate		1.80%	1.80%
Derivative, Lower Range of Effective Rate, Variable Rate		3.29%	3.29%
Derivative, Upper Range of Effective Rate, Variable Rate		3.94%	3.94%
Consolidated Subsidiaries Interest Rate Swap 1 [Domain] | London Interbank Offered Rate (LIBOR) [Member]
Cash flow hedges of interest rate risk [Abstract]
Debt Instrument, Description of Variable Rate Basis		one-month LIBOR
Consolidated Subsidiaries Interest Rate Swap 2 [Domain]
Cash flow hedges of interest rate risk [Abstract]
Noncontrolling Interest, Ownership Percentage by Parent		100.00%	100.00%
Derivative, Notional Amount		$ 100,000
Derivative, Fixed Interest Rate		2.14%	2.14%
Derivative, Basis Spread on Variable Rate		1.55%	1.55%
Total Swapped Rate On Loan		3.69%	3.69%
Derivative, Maturity Date		Feb. 01, 2022
Consolidated Subsidiaries Interest Rate Swap 2 [Domain] | Unsecured Debt 275M Term Loan [Member]
Cash flow hedges of interest rate risk [Abstract]
Unsecured Debt		$ 275,000
Derivative, Lower Range of Basis Spread, Variable Rate		1.15%	1.15%
Derivative, Higher Range of Basis Spread, Variable Rate		1.80%	1.80%
Derivative, Lower Range of Effective Rate, Variable Rate		3.29%	3.29%
Derivative, Upper Range of Effective Rate, Variable Rate		3.94%	3.94%
Consolidated Subsidiaries Interest Rate Swap 2 [Domain] | London Interbank Offered Rate (LIBOR) [Member]
Cash flow hedges of interest rate risk [Abstract]
Debt Instrument, Description of Variable Rate Basis		one-month LIBOR
Consolidated Subsidiaries Interest Rate Swap 3 [Domain]
Cash flow hedges of interest rate risk [Abstract]
Noncontrolling Interest, Ownership Percentage by Parent		100.00%	100.00%
Derivative, Notional Amount		$ 50,000
Derivative, Fixed Interest Rate		2.14%	2.14%
Derivative, Basis Spread on Variable Rate		1.55%	1.55%
Total Swapped Rate On Loan		3.69%	3.69%
Derivative, Maturity Date		Feb. 01, 2022
Consolidated Subsidiaries Interest Rate Swap 3 [Domain] | Unsecured Debt 275M Term Loan [Member]
Cash flow hedges of interest rate risk [Abstract]
Unsecured Debt		$ 275,000
Derivative, Lower Range of Basis Spread, Variable Rate		1.15%	1.15%
Derivative, Higher Range of Basis Spread, Variable Rate		1.80%	1.80%
Derivative, Lower Range of Effective Rate, Variable Rate		3.29%	3.29%
Derivative, Upper Range of Effective Rate, Variable Rate		3.94%	3.94%
Consolidated Subsidiaries Interest Rate Swap 3 [Domain] | London Interbank Offered Rate (LIBOR) [Member]
Cash flow hedges of interest rate risk [Abstract]
Debt Instrument, Description of Variable Rate Basis		one-month LIBOR
Consolidated Subsidiaries Interest Rate Swap 4 [Domain]
Cash flow hedges of interest rate risk [Abstract]
Noncontrolling Interest, Ownership Percentage by Parent		100.00%	100.00%
Derivative, Notional Amount		$ 50,000
Derivative, Fixed Interest Rate		2.14%	2.14%
Derivative, Maturity Date		Feb. 01, 2022
Consolidated Subsidiaries Interest Rate Swap 4 [Domain] | Line of Credit [Member]
Cash flow hedges of interest rate risk [Abstract]
Derivative, Basis Spread on Variable Rate		1.38%	1.38%
Total Swapped Rate On Loan		3.51%	3.51%
Unsecured Debt		$ 25,000
Line of Credit Facility, Maximum Borrowing Capacity		$ 1,100,000
Derivative, Lower Range of Basis Spread, Variable Rate		1.05%	1.05%
Derivative, Higher Range of Basis Spread, Variable Rate		1.60%	1.60%
Derivative, Lower Range of Effective Rate, Variable Rate		3.19%	3.19%
Derivative, Upper Range of Effective Rate, Variable Rate		3.74%	3.74%
Consolidated Subsidiaries Interest Rate Swap 4 [Domain] | Unsecured Debt 275M Term Loan [Member]
Cash flow hedges of interest rate risk [Abstract]
Derivative, Basis Spread on Variable Rate		1.55%	1.55%
Total Swapped Rate On Loan		3.69%	3.69%
Unsecured Debt		$ 275,000
Derivative, Lower Range of Basis Spread, Variable Rate		1.15%	1.15%
Derivative, Higher Range of Basis Spread, Variable Rate		1.80%	1.80%
Derivative, Lower Range of Effective Rate, Variable Rate		3.29%	3.29%
Derivative, Upper Range of Effective Rate, Variable Rate		3.94%	3.94%
Consolidated Subsidiaries Interest Rate Swap 4 [Domain] | London Interbank Offered Rate (LIBOR) [Member]
Cash flow hedges of interest rate risk [Abstract]
Debt Instrument, Description of Variable Rate Basis		one-month LIBOR
Consolidated Subsidiaries Interest Rate Swap 5 [Domain]
Cash flow hedges of interest rate risk [Abstract]
Noncontrolling Interest, Ownership Percentage by Parent		100.00%	100.00%
Derivative, Notional Amount		$ 125,000
Derivative, Fixed Interest Rate		3.02%	3.02%
Derivative, Basis Spread on Variable Rate		1.60%	1.60%
Total Swapped Rate On Loan		4.62%	4.62%
Derivative, Maturity Date		Mar. 01, 2023
Unsecured Debt		$ 250,000
Derivative, Lower Range of Basis Spread, Variable Rate		1.25%	1.25%
Derivative, Higher Range of Basis Spread, Variable Rate		1.90%	1.90%
Derivative, Lower Range of Effective Rate, Variable Rate		4.27%	4.27%
Derivative, Upper Range of Effective Rate, Variable Rate		4.92%	4.92%
Consolidated Subsidiaries Interest Rate Swap 5 [Domain] | London Interbank Offered Rate (LIBOR) [Member]
Cash flow hedges of interest rate risk [Abstract]
Debt Instrument, Description of Variable Rate Basis		one-month LIBOR
Consolidated Subsidiaries Interest Rate Swap 6 [Domain]
Cash flow hedges of interest rate risk [Abstract]
Noncontrolling Interest, Ownership Percentage by Parent		100.00%	100.00%
Derivative, Notional Amount		$ 75,000
Derivative, Fixed Interest Rate		3.02%	3.02%
Derivative, Basis Spread on Variable Rate		1.60%	1.60%
Total Swapped Rate On Loan		4.62%	4.62%
Derivative, Maturity Date		Mar. 01, 2023
Unsecured Debt		$ 250,000
Derivative, Lower Range of Basis Spread, Variable Rate		1.25%	1.25%
Derivative, Higher Range of Basis Spread, Variable Rate		1.90%	1.90%
Derivative, Lower Range of Effective Rate, Variable Rate		4.27%	4.27%
Derivative, Upper Range of Effective Rate, Variable Rate		4.92%	4.92%
Consolidated Subsidiaries Interest Rate Swap 6 [Domain] | London Interbank Offered Rate (LIBOR) [Member]
Cash flow hedges of interest rate risk [Abstract]
Debt Instrument, Description of Variable Rate Basis		one-month LIBOR
Consolidated Subsidiaries Interest Rate Swap 7 [Domain]
Cash flow hedges of interest rate risk [Abstract]
Noncontrolling Interest, Ownership Percentage by Parent		100.00%	100.00%
Derivative, Notional Amount		$ 50,000
Derivative, Fixed Interest Rate		3.02%	3.02%
Derivative, Basis Spread on Variable Rate		1.60%	1.60%
Total Swapped Rate On Loan		4.62%	4.62%
Derivative, Maturity Date		Mar. 01, 2023
Unsecured Debt		$ 250,000
Derivative, Lower Range of Basis Spread, Variable Rate		1.25%	1.25%
Derivative, Higher Range of Basis Spread, Variable Rate		1.90%	1.90%
Derivative, Lower Range of Effective Rate, Variable Rate		4.27%	4.27%
Derivative, Upper Range of Effective Rate, Variable Rate		4.92%	4.92%
Consolidated Subsidiaries Interest Rate Swap 7 [Domain] | London Interbank Offered Rate (LIBOR) [Member]
Cash flow hedges of interest rate risk [Abstract]
Debt Instrument, Description of Variable Rate Basis		one-month LIBOR
Consolidated Subsidiaries Interest Rate Swap 8 [Domain]
Cash flow hedges of interest rate risk [Abstract]
Noncontrolling Interest, Ownership Percentage by Parent		100.00%	100.00%
Derivative, Notional Amount		$ 12,000
Derivative, Fixed Interest Rate		2.09%	2.09%
Derivative, Basis Spread on Variable Rate		1.40%	1.40%
Total Swapped Rate On Loan		3.49%	3.49%
Derivative, Maturity Date		Mar. 01, 2024
Unconsolidated Joint Ventures Interest Rate Swap 1 [Member]
Cash flow hedges of interest rate risk [Abstract]
Noncontrolling Interest, Ownership Percentage by Parent		50.10%	50.10%
Derivative, Notional Amount		$ 156,734
Derivative, Fixed Interest Rate		1.83%	1.83%
Derivative, Basis Spread on Variable Rate		1.75%	1.75%
Total Swapped Rate On Loan		3.58%	3.58%
Derivative, Maturity Date		Dec. 01, 2021
Unconsolidated Joint Ventures Interest Rate Swap 2 (Member)
Cash flow hedges of interest rate risk [Abstract]
Noncontrolling Interest, Ownership Percentage by Parent		17.15%	17.15%
Derivative, Notional Amount		$ 52,065	₩ 60,500,000
Derivative, Fixed Interest Rate		1.52%	1.52%
Derivative, Basis Spread on Variable Rate		1.60%	1.60%
Total Swapped Rate On Loan		3.12%	3.12%
Derivative, Maturity Date		Sep. 01, 2020
Swapped Foreign Currency Exchange Rate		1,162.0