Derivative and Hedging Activities (Interest Rate Derivatives) (Details) ₩ in Thousands, $ in Thousands | 3 Months Ended | 9 Months Ended | |
Sep. 30, 2016USD ($) | Sep. 30, 2017USD ($) | Sep. 30, 2016USD ($) | Sep. 30, 2017KRW (₩) |
Cash flow hedges of interest rate risk [Abstract] | | | | |
Noncontrolling Interest, Ownership Percentage by Parent | | 71.00% | | 71.00% |
Unsecured Debt [Member] | | | | |
Derivative [Line Items] | | | | |
Derivative, Net Hedge Ineffectiveness Gain (Loss) | $ 500 | | $ 200 | |
Cash flow hedges of interest rate risk [Abstract] | | | | |
Unsecured Debt | | $ 475,000 | | |
Consolidated Subsidiaries Interest Rate Swap 1 [Domain] | | | | |
Derivative [Line Items] | | | | |
Derivative, Lower Range of Effective Rate, Variable Rate | | 2.99% | | 2.99% |
Derivative, Upper Range of Effective Rate, Variable Rate | | 3.54% | | 3.54% |
Cash flow hedges of interest rate risk [Abstract] | | | | |
Noncontrolling Interest, Ownership Percentage by Parent | | 100.00% | | 100.00% |
Derivative, Notional Amount | | $ 200,000 | | |
Derivative, Fixed Interest Rate | | 1.64% | | 1.64% |
Derivative, Basis Spread on Variable Rate | | 1.45% | | 1.45% |
Total Swapped Rate On Loan | | 3.09% | | 3.09% |
Derivative, Maturity Date | | Feb. 1, 2019 | | |
Unsecured Debt | | $ 475,000 | | |
Derivative, Lower Range of Basis Spread, Variable Rate | | 1.35% | | 1.35% |
Derivative, Higher Range of Basis Spread, Variable Rate | | 1.90% | | 1.90% |
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] | | | | |
Derivative [Line Items] | | | | |
Derivative, Lower Range of Effective Rate, Variable Rate | | 3.00% | | 3.00% |
Derivative, Upper Range of Effective Rate, Variable Rate | | 3.55% | | 3.55% |
Cash flow hedges of interest rate risk [Abstract] | | | | |
Noncontrolling Interest, Ownership Percentage by Parent | | 100.00% | | 100.00% |
Derivative, Notional Amount | | $ 175,000 | | |
Derivative, Fixed Interest Rate | | 1.65% | | 1.65% |
Derivative, Basis Spread on Variable Rate | | 1.45% | | 1.45% |
Total Swapped Rate On Loan | | 3.10% | | 3.10% |
Derivative, Maturity Date | | Feb. 1, 2019 | | |
Unsecured Debt | | $ 475,000 | | |
Derivative, Lower Range of Basis Spread, Variable Rate | | 1.35% | | 1.35% |
Derivative, Higher Range of Basis Spread, Variable Rate | | 1.90% | | 1.90% |
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] | | | | |
Derivative [Line Items] | | | | |
Derivative, Lower Range of Effective Rate, Variable Rate | | 2.99% | | 2.99% |
Derivative, Upper Range of Effective Rate, Variable Rate | | 3.54% | | 3.54% |
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 | | 1.64% | | 1.64% |
Derivative, Basis Spread on Variable Rate | | 1.45% | | 1.45% |
Total Swapped Rate On Loan | | 3.09% | | 3.09% |
Derivative, Maturity Date | | Feb. 1, 2019 | | |
Unsecured Debt | | $ 475,000 | | |
Derivative, Lower Range of Basis Spread, Variable Rate | | 1.35% | | 1.35% |
Derivative, Higher Range of Basis Spread, Variable Rate | | 1.90% | | 1.90% |
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] | | | | |
Derivative [Line Items] | | | | |
Derivative, Lower Range of Effective Rate, Variable Rate | | 3.39% | | 3.39% |
Derivative, Upper Range of Effective Rate, Variable Rate | | 4.04% | | 4.04% |
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 | | | | |
Total Swapped Rate On Loan | | | | |
Derivative, Maturity Date | | Feb. 1, 2022 | | |
Unsecured Debt | | $ 300,000 | | |
Derivative, Effective Date | | Jan. 1, 2018 | | |
Derivative, Lower Range of Basis Spread, Variable Rate | | 1.25% | | 1.25% |
Derivative, Higher Range of Basis Spread, Variable Rate | | 1.90% | | 1.90% |
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] | | | | |
Derivative [Line Items] | | | | |
Derivative, Lower Range of Effective Rate, Variable Rate | | 3.39% | | 3.39% |
Derivative, Upper Range of Effective Rate, Variable Rate | | 4.04% | | 4.04% |
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 | | | | |
Total Swapped Rate On Loan | | | | |
Derivative, Maturity Date | | Feb. 1, 2022 | | |
Unsecured Debt | | $ 300,000 | | |
Derivative, Lower Range of Basis Spread, Variable Rate | | 1.25% | | 1.25% |
Derivative, Higher Range of Basis Spread, Variable Rate | | 1.90% | | 1.90% |
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] | | | | |
Derivative [Line Items] | | | | |
Derivative, Lower Range of Effective Rate, Variable Rate | | 3.39% | | 3.39% |
Derivative, Upper Range of Effective Rate, Variable Rate | | 4.04% | | 4.04% |
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 | | | | |
Total Swapped Rate On Loan | | | | |
Derivative, Maturity Date | | Feb. 1, 2022 | | |
Unsecured Debt | | $ 300,000 | | |
Derivative, Lower Range of Basis Spread, Variable Rate | | 1.25% | | 1.25% |
Derivative, Higher Range of Basis Spread, Variable Rate | | 1.90% | | 1.90% |
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] | | | | |
Derivative [Line Items] | | | | |
Derivative, Lower Range of Effective Rate, Variable Rate | | 3.39% | | 3.39% |
Derivative, Upper Range of Effective Rate, Variable Rate | | 4.04% | | 4.04% |
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 | | | | |
Total Swapped Rate On Loan | | | | |
Derivative, Maturity Date | | Feb. 1, 2022 | | |
Unsecured Debt | | $ 300,000 | | |
Derivative, Lower Range of Basis Spread, Variable Rate | | 1.25% | | 1.25% |
Derivative, Higher Range of Basis Spread, Variable Rate | | 1.90% | | 1.90% |
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. 1, 2024 | | |
Unconsolidated Joint Ventures Interest Rate Swap 1 [Member] | | | | |
Cash flow hedges of interest rate risk [Abstract] | | | | |
Noncontrolling Interest, Ownership Percentage by Parent | | 50.00% | | 50.00% |
Derivative, Notional Amount | | $ 130,801 | | |
Derivative, Fixed Interest Rate | | 2.40% | | 2.40% |
Derivative, Basis Spread on Variable Rate | | 1.70% | | 1.70% |
Total Swapped Rate On Loan | | 4.10% | | 4.10% |
Derivative, Maturity Date | | Apr. 1, 2018 | | |
Unconsolidated Joint Ventures Interest Rate Swap 2 (Member) | | | | |
Cash flow hedges of interest rate risk [Abstract] | | | | |
Noncontrolling Interest, Ownership Percentage by Parent | | 50.00% | | 50.00% |
Derivative, Notional Amount | | $ 130,801 | | |
Derivative, Fixed Interest Rate | | 2.40% | | 2.40% |
Derivative, Basis Spread on Variable Rate | | 1.70% | | 1.70% |
Total Swapped Rate On Loan | | 4.10% | | 4.10% |
Derivative, Maturity Date | | Apr. 1, 2018 | | |
Unconsolidated Joint Ventures Interest Rate Swap3 [Member] | | | | |
Cash flow hedges of interest rate risk [Abstract] | | | | |
Noncontrolling Interest, Ownership Percentage by Parent | | 50.10% | | 50.10% |
Derivative, Notional Amount | | $ 166,500 | | |
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. 1, 2021 | | |
Unconsolidated Joint Ventures Interest Rate Swap 4 [Member] | | | | |
Cash flow hedges of interest rate risk [Abstract] | | | | |
Noncontrolling Interest, Ownership Percentage by Parent | | 34.30% | | 34.30% |
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. 1, 2020 | | |
Swapped Foreign Currency Exchange Rate | | 1,162 | | |