Shareholder Report, Holdings (Details)	Nov. 30, 2024
C000001854 [Member] | US Government Debt Securities Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	20.10%
C000001854 [Member] | Moody's, Aaa Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.50%
C000001854 [Member] | US Government Corporations and Agencies Securities Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	34.70%
C000001854 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.70%
C000001854 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	6.70%
C000001854 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	21.60%
C000001854 [Member] | Standard & Poor's, BB Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	7.60%
C000001854 [Member] | Standard & Poor's, B Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.80%
C000001854 [Member] | CCC and below [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.20%
C000001854 [Member] | Not Rated [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.20%
C000001854 [Member] | Short term investments and other Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.00%
C000001854 [Member] | Mortgage Backed Securities Issued by US Government Sponsored Enterprises Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.90%
C000001854 [Member] | Asset-Backed Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	4.60%
C000001854 [Member] | Corporate Bond Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	36.30%
C000001854 [Member] | Mortgage-Backed Securities, Issued by Private Enterprises [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.40%
C000001854 [Member] | Mortgage-Backed Securities, Issued by US Government Sponsored Enterprises [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.90%
C000001854 [Member] | US Government Corporations and Agencies Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	34.70%
C000001854 [Member] | US Government Debt Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	20.10%
C000001854 [Member] | Short term investments and other [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.00%
C000001856 [Member] | US Government Debt Securities Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	20.10%
C000001856 [Member] | Moody's, Aaa Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.50%
C000001856 [Member] | US Government Corporations and Agencies Securities Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	34.70%
C000001856 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.70%
C000001856 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	6.70%
C000001856 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	21.60%
C000001856 [Member] | Standard & Poor's, BB Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	7.60%
C000001856 [Member] | Standard & Poor's, B Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.80%
C000001856 [Member] | CCC and below [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.20%
C000001856 [Member] | Not Rated [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.20%
C000001856 [Member] | Short term investments and other Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.00%
C000001856 [Member] | Mortgage Backed Securities Issued by US Government Sponsored Enterprises Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.90%
C000001856 [Member] | Asset-Backed Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	4.60%
C000001856 [Member] | Corporate Bond Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	36.30%
C000001856 [Member] | Mortgage-Backed Securities, Issued by Private Enterprises [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.40%
C000001856 [Member] | Mortgage-Backed Securities, Issued by US Government Sponsored Enterprises [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.90%
C000001856 [Member] | US Government Corporations and Agencies Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	34.70%
C000001856 [Member] | US Government Debt Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	20.10%
C000001856 [Member] | Short term investments and other [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.00%
C000001857 [Member] | US Government Debt Securities Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	20.10%
C000001857 [Member] | Moody's, Aaa Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.50%
C000001857 [Member] | US Government Corporations and Agencies Securities Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	34.70%
C000001857 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.70%
C000001857 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	6.70%
C000001857 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	21.60%
C000001857 [Member] | Standard & Poor's, BB Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	7.60%
C000001857 [Member] | Standard & Poor's, B Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.80%
C000001857 [Member] | CCC and below [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.20%
C000001857 [Member] | Not Rated [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.20%
C000001857 [Member] | Short term investments and other Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.00%
C000001857 [Member] | Mortgage Backed Securities Issued by US Government Sponsored Enterprises Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.90%
C000001857 [Member] | Asset-Backed Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	4.60%
C000001857 [Member] | Corporate Bond Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	36.30%
C000001857 [Member] | Mortgage-Backed Securities, Issued by Private Enterprises [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.40%
C000001857 [Member] | Mortgage-Backed Securities, Issued by US Government Sponsored Enterprises [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.90%
C000001857 [Member] | US Government Corporations and Agencies Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	34.70%
C000001857 [Member] | US Government Debt Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	20.10%
C000001857 [Member] | Short term investments and other [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.00%
C000153977 [Member] | US Government Debt Securities Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	20.10%
C000153977 [Member] | Moody's, Aaa Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.50%
C000153977 [Member] | US Government Corporations and Agencies Securities Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	34.70%
C000153977 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.70%
C000153977 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	6.70%
C000153977 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	21.60%
C000153977 [Member] | Standard & Poor's, BB Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	7.60%
C000153977 [Member] | Standard & Poor's, B Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.80%
C000153977 [Member] | CCC and below [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.20%
C000153977 [Member] | Not Rated [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.20%
C000153977 [Member] | Short term investments and other Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.00%
C000153977 [Member] | Mortgage Backed Securities Issued by US Government Sponsored Enterprises Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.90%
C000153977 [Member] | Asset-Backed Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	4.60%
C000153977 [Member] | Corporate Bond Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	36.30%
C000153977 [Member] | Mortgage-Backed Securities, Issued by Private Enterprises [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.40%
C000153977 [Member] | Mortgage-Backed Securities, Issued by US Government Sponsored Enterprises [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.90%
C000153977 [Member] | US Government Corporations and Agencies Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	34.70%
C000153977 [Member] | US Government Debt Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	20.10%
C000153977 [Member] | Short term investments and other [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.00%
C000113488 [Member] | US Government Debt Securities Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	20.10%
C000113488 [Member] | Moody's, Aaa Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.50%
C000113488 [Member] | US Government Corporations and Agencies Securities Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	34.70%
C000113488 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.70%
C000113488 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	6.70%
C000113488 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	21.60%
C000113488 [Member] | Standard & Poor's, BB Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	7.60%
C000113488 [Member] | Standard & Poor's, B Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.80%
C000113488 [Member] | CCC and below [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.20%
C000113488 [Member] | Not Rated [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.20%
C000113488 [Member] | Short term investments and other Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.00%
C000113488 [Member] | Mortgage Backed Securities Issued by US Government Sponsored Enterprises Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.90%
C000113488 [Member] | Asset-Backed Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	4.60%
C000113488 [Member] | Corporate Bond Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	36.30%
C000113488 [Member] | Mortgage-Backed Securities, Issued by Private Enterprises [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.40%
C000113488 [Member] | Mortgage-Backed Securities, Issued by US Government Sponsored Enterprises [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.90%
C000113488 [Member] | US Government Corporations and Agencies Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	34.70%
C000113488 [Member] | US Government Debt Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	20.10%
C000113488 [Member] | Short term investments and other [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.00%
C000153978 [Member] | US Government Debt Securities Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	20.10%
C000153978 [Member] | Moody's, Aaa Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.50%
C000153978 [Member] | US Government Corporations and Agencies Securities Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	34.70%
C000153978 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.70%
C000153978 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	6.70%
C000153978 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	21.60%
C000153978 [Member] | Standard & Poor's, BB Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	7.60%
C000153978 [Member] | Standard & Poor's, B Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.80%
C000153978 [Member] | CCC and below [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.20%
C000153978 [Member] | Not Rated [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.20%
C000153978 [Member] | Short term investments and other Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.00%
C000153978 [Member] | Mortgage Backed Securities Issued by US Government Sponsored Enterprises Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.90%
C000153978 [Member] | Asset-Backed Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	4.60%
C000153978 [Member] | Corporate Bond Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	36.30%
C000153978 [Member] | Mortgage-Backed Securities, Issued by Private Enterprises [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.40%
C000153978 [Member] | Mortgage-Backed Securities, Issued by US Government Sponsored Enterprises [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.90%
C000153978 [Member] | US Government Corporations and Agencies Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	34.70%
C000153978 [Member] | US Government Debt Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	20.10%
C000153978 [Member] | Short term investments and other [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.00%
C000106442 [Member] | US Government Debt Securities Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	20.10%
C000106442 [Member] | Moody's, Aaa Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.50%
C000106442 [Member] | US Government Corporations and Agencies Securities Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	34.70%
C000106442 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.70%
C000106442 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	6.70%
C000106442 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	21.60%
C000106442 [Member] | Standard & Poor's, BB Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	7.60%
C000106442 [Member] | Standard & Poor's, B Rating [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.80%
C000106442 [Member] | CCC and below [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.20%
C000106442 [Member] | Not Rated [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.20%
C000106442 [Member] | Short term investments and other Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.00%
C000106442 [Member] | Mortgage Backed Securities Issued by US Government Sponsored Enterprises Quality [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.90%
C000106442 [Member] | Asset-Backed Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	4.60%
C000106442 [Member] | Corporate Bond Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	36.30%
C000106442 [Member] | Mortgage-Backed Securities, Issued by Private Enterprises [Member]
Holdings [Line Items]
Percent of Net Asset Value	2.40%
C000106442 [Member] | Mortgage-Backed Securities, Issued by US Government Sponsored Enterprises [Member]
Holdings [Line Items]
Percent of Net Asset Value	0.90%
C000106442 [Member] | US Government Corporations and Agencies Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	34.70%
C000106442 [Member] | US Government Debt Securities [Member]
Holdings [Line Items]
Percent of Net Asset Value	20.10%
C000106442 [Member] | Short term investments and other [Member]
Holdings [Line Items]
Percent of Net Asset Value	1.00%